diff --git a/locale/circuitpython.pot b/locale/circuitpython.pot
index 77d5aab1d3..f87fc02975 100644
--- a/locale/circuitpython.pot
+++ b/locale/circuitpython.pot
@@ -193,6 +193,10 @@ msgstr ""
 msgid "%q must be array of type 'H'"
 msgstr ""
 
+#: shared-bindings/synthio/MidiTrack.c shared-bindings/synthio/__init__.c
+msgid "%q must be array of type 'h'"
+msgstr ""
+
 #: ports/raspberrypi/bindings/cyw43/__init__.c py/argcheck.c py/objexcept.c
 #: shared-bindings/canio/CAN.c shared-bindings/digitalio/Pull.c
 msgid "%q must be of type %q or %q, not %q"
diff --git a/ports/atmel-samd/boards/pewpew_m4/mpconfigboard.mk b/ports/atmel-samd/boards/pewpew_m4/mpconfigboard.mk
index f7e7be88d5..49be084ddf 100644
--- a/ports/atmel-samd/boards/pewpew_m4/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/pewpew_m4/mpconfigboard.mk
@@ -44,6 +44,8 @@ CIRCUITPY_AUDIOIO = 1
 CIRCUITPY_AUDIOMIXER = 1
 CIRCUITPY_DISPLAYIO = 1
 CIRCUITPY_KEYPAD = 1
+CIRCUITPY_KEYPAD_SHIFTREGISTERKEYS = 0
+CIRCUITPY_KEYPAD_KEYMATRIX = 0
 CIRCUITPY_MATH = 1
 CIRCUITPY_STAGE = 1
 CIRCUITPY_SYNTHIO = 1
diff --git a/ports/mimxrt10xx/Makefile b/ports/mimxrt10xx/Makefile
index ff2b6c35c1..72f4d191ef 100644
--- a/ports/mimxrt10xx/Makefile
+++ b/ports/mimxrt10xx/Makefile
@@ -38,7 +38,6 @@ INC += \
 	-Iboards/$(BOARD) \
 	-Iperipherals/ \
 	-Iperipherals/mimxrt10xx/ \
-	-Isdk/CMSIS/Include \
 	-Isdk/devices/$(CHIP_FAMILY) \
 	-Isdk/devices/$(CHIP_FAMILY)/drivers \
 	-Isdk/drivers/common
diff --git a/ports/mimxrt10xx/mpconfigport.mk b/ports/mimxrt10xx/mpconfigport.mk
index b03535b6b2..ae22cb69f4 100644
--- a/ports/mimxrt10xx/mpconfigport.mk
+++ b/ports/mimxrt10xx/mpconfigport.mk
@@ -18,6 +18,7 @@ CIRCUITPY_AUDIOIO = 0
 CIRCUITPY_AUDIOMIXER = 1
 CIRCUITPY_AUDIOMP3 = 1
 CIRCUITPY_AUDIOPWMIO = 1
+CIRCUITPY_SYNTHIO_MAX_CHANNELS = 12
 CIRCUITPY_BUSDEVICE = 1
 CIRCUITPY_COUNTIO = 0
 CIRCUITPY_FREQUENCYIO = 0
diff --git a/ports/raspberrypi/mpconfigport.mk b/ports/raspberrypi/mpconfigport.mk
index 21dde6d239..671d4669bf 100644
--- a/ports/raspberrypi/mpconfigport.mk
+++ b/ports/raspberrypi/mpconfigport.mk
@@ -19,6 +19,7 @@ CIRCUITPY_PWMIO ?= 1
 CIRCUITPY_RGBMATRIX ?= $(CIRCUITPY_DISPLAYIO)
 CIRCUITPY_ROTARYIO ?= 1
 CIRCUITPY_ROTARYIO_SOFTENCODER = 1
+CIRCUITPY_SYNTHIO_MAX_CHANNELS = 12
 
 # Things that need to be implemented.
 # Use PWM internally
diff --git a/ports/unix/variants/coverage/mpconfigvariant.mk b/ports/unix/variants/coverage/mpconfigvariant.mk
index 20320916bc..854d052c6c 100644
--- a/ports/unix/variants/coverage/mpconfigvariant.mk
+++ b/ports/unix/variants/coverage/mpconfigvariant.mk
@@ -30,15 +30,30 @@ SRC_BITMAP := \
 	displayio_min.c \
 	shared-bindings/aesio/aes.c \
 	shared-bindings/aesio/__init__.c \
+	shared-bindings/audiocore/__init__.c \
+	shared-bindings/audiocore/RawSample.c \
+	shared-bindings/audiocore/WaveFile.c \
+	shared-bindings/audiomixer/__init__.c \
+	shared-bindings/audiomixer/Mixer.c \
+	shared-bindings/audiomixer/MixerVoice.c \
 	shared-bindings/bitmaptools/__init__.c \
 	shared-bindings/displayio/Bitmap.c \
 	shared-bindings/rainbowio/__init__.c \
 	shared-bindings/struct/__init__.c \
+	shared-bindings/synthio/__init__.c \
+	shared-bindings/synthio/MidiTrack.c \
+	shared-bindings/synthio/Synthesizer.c \
 	shared-bindings/traceback/__init__.c \
 	shared-bindings/util.c \
 	shared-bindings/zlib/__init__.c \
 	shared-module/aesio/aes.c \
 	shared-module/aesio/__init__.c \
+	shared-module/audiocore/__init__.c \
+	shared-module/audiocore/RawSample.c \
+	shared-module/audiocore/WaveFile.c \
+	shared-module/audiomixer/__init__.c \
+	shared-module/audiomixer/Mixer.c \
+	shared-module/audiomixer/MixerVoice.c \
 	shared-module/bitmaptools/__init__.c \
 	shared-module/displayio/area.c \
 	shared-module/displayio/Bitmap.c \
@@ -47,6 +62,9 @@ SRC_BITMAP := \
 	shared-module/os/getenv.c \
 	shared-module/rainbowio/__init__.c \
 	shared-module/struct/__init__.c \
+	shared-module/synthio/__init__.c \
+	shared-module/synthio/MidiTrack.c \
+	shared-module/synthio/Synthesizer.c \
 	shared-module/traceback/__init__.c \
 	shared-module/zlib/__init__.c \
 
@@ -54,12 +72,17 @@ SRC_C += $(SRC_BITMAP)
 
 CFLAGS += \
 	-DCIRCUITPY_AESIO=1 \
+	-DCIRCUITPY_AUDIOCORE=1 \
+	-DCIRCUITPY_AUDIOMIXER=1 \
+	-DCIRCUITPY_AUDIOCORE_DEBUG=1 \
 	-DCIRCUITPY_BITMAPTOOLS=1 \
 	-DCIRCUITPY_DISPLAYIO_UNIX=1 \
-	-DCIRCUITPY_OS_GETENV=1 \
 	-DCIRCUITPY_GIFIO=1 \
+	-DCIRCUITPY_OS_GETENV=1 \
 	-DCIRCUITPY_RAINBOWIO=1 \
 	-DCIRCUITPY_STRUCT=1 \
+	-DCIRCUITPY_SYNTHIO=1 \
+	-DCIRCUITPY_SYNTHIO_MAX_CHANNELS=14 \
 	-DCIRCUITPY_TRACEBACK=1 \
 	-DCIRCUITPY_ZLIB=1
 
diff --git a/py/circuitpy_defns.mk b/py/circuitpy_defns.mk
index 94377238a0..fb5d745ebb 100644
--- a/py/circuitpy_defns.mk
+++ b/py/circuitpy_defns.mk
@@ -648,6 +648,7 @@ SRC_SHARED_MODULE_ALL = \
 	supervisor/__init__.c \
 	supervisor/StatusBar.c \
 	synthio/MidiTrack.c \
+	synthio/Synthesizer.c \
 	synthio/__init__.c \
 	terminalio/Terminal.c \
 	terminalio/__init__.c \
diff --git a/py/circuitpy_mpconfig.mk b/py/circuitpy_mpconfig.mk
index b8e2178870..0aec2ebe74 100644
--- a/py/circuitpy_mpconfig.mk
+++ b/py/circuitpy_mpconfig.mk
@@ -107,6 +107,11 @@ CFLAGS += -DCIRCUITPY_AUDIOCORE=$(CIRCUITPY_AUDIOCORE)
 CIRCUITPY_AUDIOMIXER ?= $(CIRCUITPY_AUDIOIO)
 CFLAGS += -DCIRCUITPY_AUDIOMIXER=$(CIRCUITPY_AUDIOMIXER)
 
+ifndef CIRCUITPY_AUDIOCORE_DEBUG
+CIRCUITPY_AUDIOCORE_DEBUG ?= 0
+endif
+CFLAGS += -DCIRCUITPY_AUDIOCORE_DEBUG=$(CIRCUITPY_AUDIOCORE_DEBUG)
+
 ifndef CIRCUITPY_AUDIOMP3
 ifeq ($(CIRCUITPY_FULL_BUILD),1)
 CIRCUITPY_AUDIOMP3 = $(CIRCUITPY_AUDIOCORE)
@@ -286,6 +291,15 @@ CFLAGS += -DCIRCUITPY_JSON=$(CIRCUITPY_JSON)
 CIRCUITPY_KEYPAD ?= $(CIRCUITPY_FULL_BUILD)
 CFLAGS += -DCIRCUITPY_KEYPAD=$(CIRCUITPY_KEYPAD)
 
+CIRCUITPY_KEYPAD_KEYS ?= $(CIRCUITPY_KEYPAD)
+CFLAGS += -DCIRCUITPY_KEYPAD_KEYS=$(CIRCUITPY_KEYPAD_KEYS)
+
+CIRCUITPY_KEYPAD_KEYMATRIX ?= $(CIRCUITPY_KEYPAD)
+CFLAGS += -DCIRCUITPY_KEYPAD_KEYMATRIX=$(CIRCUITPY_KEYPAD_KEYMATRIX)
+
+CIRCUITPY_KEYPAD_SHIFTREGISTERKEYS ?= $(CIRCUITPY_KEYPAD)
+CFLAGS += -DCIRCUITPY_KEYPAD_SHIFTREGISTERKEYS=$(CIRCUITPY_KEYPAD_SHIFTREGISTERKEYS)
+
 CIRCUITPY_MATH ?= 1
 CFLAGS += -DCIRCUITPY_MATH=$(CIRCUITPY_MATH)
 
@@ -437,6 +451,10 @@ CFLAGS += -DCIRCUITPY_SUPERVISOR=$(CIRCUITPY_SUPERVISOR)
 CIRCUITPY_SYNTHIO ?= $(CIRCUITPY_AUDIOCORE)
 CFLAGS += -DCIRCUITPY_SYNTHIO=$(CIRCUITPY_SYNTHIO)
 
+CIRCUITPY_SYNTHIO_MAX_CHANNELS ?= 2
+CFLAGS += -DCIRCUITPY_SYNTHIO_MAX_CHANNELS=$(CIRCUITPY_SYNTHIO_MAX_CHANNELS)
+
+
 CIRCUITPY_SYS ?= 1
 CFLAGS += -DCIRCUITPY_SYS=$(CIRCUITPY_SYS)
 
diff --git a/shared-bindings/audiobusio/I2SOut.c b/shared-bindings/audiobusio/I2SOut.c
index 3713caeb7b..8c6f1a3a7a 100644
--- a/shared-bindings/audiobusio/I2SOut.c
+++ b/shared-bindings/audiobusio/I2SOut.c
@@ -97,7 +97,7 @@
 //|         ...
 STATIC mp_obj_t audiobusio_i2sout_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
     #if !CIRCUITPY_AUDIOBUSIO_I2SOUT
-    mp_raise_NotImplementedError(translate("I2SOut not available"));
+    mp_raise_NotImplementedError_varg(translate("%q"), MP_QSTR_I2SOut);
     return NULL;                // Not reachable.
     #else
     enum { ARG_bit_clock, ARG_word_select, ARG_data, ARG_left_justified };
diff --git a/shared-bindings/audiobusio/PDMIn.c b/shared-bindings/audiobusio/PDMIn.c
index b6a316fadb..1f0e500292 100644
--- a/shared-bindings/audiobusio/PDMIn.c
+++ b/shared-bindings/audiobusio/PDMIn.c
@@ -94,7 +94,7 @@
 //|     ...
 STATIC mp_obj_t audiobusio_pdmin_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
     #if !CIRCUITPY_AUDIOBUSIO_PDMIN
-    mp_raise_NotImplementedError(translate("PDMIn not available"));
+    mp_raise_NotImplementedError_varg(translate("%q"), MP_QSTR_PDMIn);
     #else
     enum { ARG_clock_pin, ARG_data_pin, ARG_sample_rate, ARG_bit_depth, ARG_mono, ARG_oversample, ARG_startup_delay };
     static const mp_arg_t allowed_args[] = {
diff --git a/shared-bindings/audiocore/RawSample.c b/shared-bindings/audiocore/RawSample.c
index d185476f03..39992f87c1 100644
--- a/shared-bindings/audiocore/RawSample.c
+++ b/shared-bindings/audiocore/RawSample.c
@@ -40,7 +40,7 @@
 //|     def __init__(
 //|         self, buffer: ReadableBuffer, *, channel_count: int = 1, sample_rate: int = 8000
 //|     ) -> None:
-//|         """Create a RawSample based on the given buffer of signed values. If channel_count is more than
+//|         """Create a RawSample based on the given buffer of values. If channel_count is more than
 //|         1 then each channel's samples should alternate. In other words, for a two channel buffer, the
 //|         first sample will be for channel 1, the second sample will be for channel two, the third for
 //|         channel 1 and so on.
diff --git a/shared-bindings/audiocore/WaveFile.c b/shared-bindings/audiocore/WaveFile.c
index 36204fa2b2..3a13db72a0 100644
--- a/shared-bindings/audiocore/WaveFile.c
+++ b/shared-bindings/audiocore/WaveFile.c
@@ -32,6 +32,7 @@
 #include "shared-bindings/audiocore/WaveFile.h"
 #include "shared-bindings/util.h"
 #include "supervisor/shared/translate/translate.h"
+#include "extmod/vfs_posix.h"
 
 //| class WaveFile:
 //|     """Load a wave file for audio playback
diff --git a/shared-bindings/audiocore/__init__.c b/shared-bindings/audiocore/__init__.c
index 2e3b479cf6..6f32979099 100644
--- a/shared-bindings/audiocore/__init__.c
+++ b/shared-bindings/audiocore/__init__.c
@@ -29,7 +29,6 @@
 #include "py/obj.h"
 #include "py/runtime.h"
 
-#include "shared-bindings/microcontroller/Pin.h"
 #include "shared-bindings/audiocore/__init__.h"
 #include "shared-bindings/audiocore/RawSample.h"
 #include "shared-bindings/audiocore/WaveFile.h"
@@ -37,10 +36,57 @@
 
 //| """Support for audio samples"""
 
+#if CIRCUITPY_AUDIOCORE_DEBUG
+// (no docstrings so that the debug functions are not shown on docs.circuitpython.org)
+STATIC mp_obj_t audiocore_get_buffer(mp_obj_t sample_in) {
+    uint8_t *buffer = NULL;
+    uint32_t buffer_length = 0;
+    audioio_get_buffer_result_t gbr = audiosample_get_buffer(sample_in, false, 0, &buffer, &buffer_length);
+
+    mp_obj_t result[2] = {mp_obj_new_int_from_uint(gbr), mp_const_none};
+
+    if (gbr != GET_BUFFER_ERROR) {
+        // copies the data because the gc semantics of get_buffer are unclear
+        result[1] = mp_obj_new_bytes(buffer, buffer_length);
+    }
+
+    return mp_obj_new_tuple(2, result);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(audiocore_get_buffer_obj, audiocore_get_buffer);
+
+STATIC mp_obj_t audiocore_get_structure(mp_obj_t sample_in) {
+    bool single_buffer, samples_signed;
+    uint32_t max_buffer_length;
+    uint8_t spacing;
+
+    audiosample_get_buffer_structure(sample_in, false, &single_buffer, &samples_signed, &max_buffer_length, &spacing);
+    mp_obj_t result[4] = {
+        mp_obj_new_int_from_uint(single_buffer),
+        mp_obj_new_int_from_uint(samples_signed),
+        mp_obj_new_int_from_uint(max_buffer_length),
+        mp_obj_new_int_from_uint(spacing),
+    };
+    return mp_obj_new_tuple(4, result);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(audiocore_get_structure_obj, audiocore_get_structure);
+
+STATIC mp_obj_t audiocore_reset_buffer(mp_obj_t sample_in) {
+    audiosample_reset_buffer(sample_in, false, 0);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(audiocore_reset_buffer_obj, audiocore_reset_buffer);
+
+#endif
+
 STATIC const mp_rom_map_elem_t audiocore_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_audiocore) },
     { MP_ROM_QSTR(MP_QSTR_RawSample), MP_ROM_PTR(&audioio_rawsample_type) },
     { MP_ROM_QSTR(MP_QSTR_WaveFile), MP_ROM_PTR(&audioio_wavefile_type) },
+    #if CIRCUITPY_AUDIOCORE_DEBUG
+    { MP_ROM_QSTR(MP_QSTR_get_buffer), MP_ROM_PTR(&audiocore_get_buffer_obj) },
+    { MP_ROM_QSTR(MP_QSTR_reset_buffer), MP_ROM_PTR(&audiocore_reset_buffer_obj) },
+    { MP_ROM_QSTR(MP_QSTR_get_structure), MP_ROM_PTR(&audiocore_get_structure_obj) },
+    #endif
 };
 
 STATIC MP_DEFINE_CONST_DICT(audiocore_module_globals, audiocore_module_globals_table);
diff --git a/shared-bindings/audiomixer/Mixer.c b/shared-bindings/audiomixer/Mixer.c
index 58c618fc11..83fcc06712 100644
--- a/shared-bindings/audiomixer/Mixer.c
+++ b/shared-bindings/audiomixer/Mixer.c
@@ -33,8 +33,6 @@
 #include "py/binary.h"
 #include "py/objproperty.h"
 #include "py/runtime.h"
-#include "shared-bindings/microcontroller/Pin.h"
-#include "shared-bindings/audiocore/RawSample.h"
 #include "shared-bindings/util.h"
 #include "supervisor/shared/translate/translate.h"
 
diff --git a/shared-bindings/audiomixer/Mixer.h b/shared-bindings/audiomixer/Mixer.h
index 88592a1cb3..d04f793dde 100644
--- a/shared-bindings/audiomixer/Mixer.h
+++ b/shared-bindings/audiomixer/Mixer.h
@@ -27,9 +27,7 @@
 #ifndef MICROPY_INCLUDED_SHARED_BINDINGS_AUDIOMIXER_MIXER_H
 #define MICROPY_INCLUDED_SHARED_BINDINGS_AUDIOMIXER_MIXER_H
 
-#include "common-hal/microcontroller/Pin.h"
 #include "shared-module/audiomixer/Mixer.h"
-#include "shared-bindings/audiocore/RawSample.h"
 
 extern const mp_obj_type_t audiomixer_mixer_type;
 extern const mp_obj_type_t audiomixer_mixervoice_type;
diff --git a/shared-bindings/audiomixer/MixerVoice.c b/shared-bindings/audiomixer/MixerVoice.c
index 16a1be520f..1d6cd7f39a 100644
--- a/shared-bindings/audiomixer/MixerVoice.c
+++ b/shared-bindings/audiomixer/MixerVoice.c
@@ -32,8 +32,6 @@
 #include "py/binary.h"
 #include "py/objproperty.h"
 #include "py/runtime.h"
-#include "shared-bindings/microcontroller/Pin.h"
-#include "shared-bindings/audiocore/RawSample.h"
 #include "shared-bindings/util.h"
 #include "supervisor/shared/translate/translate.h"
 
@@ -115,7 +113,7 @@ STATIC mp_obj_t audiomixer_mixervoice_obj_set_level(size_t n_args, const mp_obj_
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    float level = mp_obj_get_float(args[ARG_level].u_obj);
+    mp_float_t level = mp_obj_get_float(args[ARG_level].u_obj);
 
     if (level > 1 || level < 0) {
         mp_raise_ValueError(translate("level must be between 0 and 1"));
diff --git a/shared-bindings/audiomixer/MixerVoice.h b/shared-bindings/audiomixer/MixerVoice.h
index bce4632760..0ff8accee4 100644
--- a/shared-bindings/audiomixer/MixerVoice.h
+++ b/shared-bindings/audiomixer/MixerVoice.h
@@ -26,9 +26,6 @@
 #ifndef SHARED_BINDINGS_AUDIOMIXER_MIXERVOICE_H_
 #define SHARED_BINDINGS_AUDIOMIXER_MIXERVOICE_H_
 
-#include "common-hal/microcontroller/Pin.h"
-#include "shared-bindings/audiocore/RawSample.h"
-
 #include "shared-module/audiomixer/MixerVoice.h"
 #include "shared-module/audiomixer/Mixer.h"
 
@@ -39,8 +36,8 @@ void common_hal_audiomixer_mixervoice_construct(audiomixer_mixervoice_obj_t *sel
 void common_hal_audiomixer_mixervoice_set_parent(audiomixer_mixervoice_obj_t *self, audiomixer_mixer_obj_t *parent);
 void common_hal_audiomixer_mixervoice_play(audiomixer_mixervoice_obj_t *self, mp_obj_t sample, bool loop);
 void common_hal_audiomixer_mixervoice_stop(audiomixer_mixervoice_obj_t *self);
-float common_hal_audiomixer_mixervoice_get_level(audiomixer_mixervoice_obj_t *self);
-void common_hal_audiomixer_mixervoice_set_level(audiomixer_mixervoice_obj_t *self, float gain);
+mp_float_t common_hal_audiomixer_mixervoice_get_level(audiomixer_mixervoice_obj_t *self);
+void common_hal_audiomixer_mixervoice_set_level(audiomixer_mixervoice_obj_t *self, mp_float_t gain);
 
 bool common_hal_audiomixer_mixervoice_get_playing(audiomixer_mixervoice_obj_t *self);
 
diff --git a/shared-bindings/audiomixer/__init__.c b/shared-bindings/audiomixer/__init__.c
index 8292be9e95..4c8068172b 100644
--- a/shared-bindings/audiomixer/__init__.c
+++ b/shared-bindings/audiomixer/__init__.c
@@ -29,7 +29,6 @@
 #include "py/obj.h"
 #include "py/runtime.h"
 
-#include "shared-bindings/microcontroller/Pin.h"
 #include "shared-bindings/audiomixer/Mixer.h"
 
 //| """Support for audio mixing"""
diff --git a/shared-bindings/keypad/Event.c b/shared-bindings/keypad/Event.c
index 8264ebe612..52c574e692 100644
--- a/shared-bindings/keypad/Event.c
+++ b/shared-bindings/keypad/Event.c
@@ -167,9 +167,9 @@ STATIC mp_obj_t keypad_event_unary_op(mp_unary_op_t op, mp_obj_t self_in) {
 
 STATIC void keypad_event_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
     keypad_event_obj_t *self = MP_OBJ_TO_PTR(self_in);
-    mp_printf(print, "<Event: key_number %d %s>",
+    mp_printf(print, "<Event: key_number %d %q>",
         common_hal_keypad_event_get_key_number(self),
-        common_hal_keypad_event_get_pressed(self) ? "pressed" : "released");
+        common_hal_keypad_event_get_pressed(self) ? MP_QSTR_pressed : MP_QSTR_released);
 }
 
 STATIC const mp_rom_map_elem_t keypad_event_locals_dict_table[] = {
diff --git a/shared-bindings/keypad/KeyMatrix.c b/shared-bindings/keypad/KeyMatrix.c
index 1c623f4bed..2209f3f68f 100644
--- a/shared-bindings/keypad/KeyMatrix.c
+++ b/shared-bindings/keypad/KeyMatrix.c
@@ -71,6 +71,7 @@
 //|         ...
 
 STATIC mp_obj_t keypad_keymatrix_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
+    #if CIRCUITPY_KEYPAD_KEYMATRIX
     keypad_keymatrix_obj_t *self = m_new_obj(keypad_keymatrix_obj_t);
     self->base.type = &keypad_keymatrix_type;
     enum { ARG_row_pins, ARG_column_pins, ARG_columns_to_anodes, ARG_interval, ARG_max_events };
@@ -114,8 +115,13 @@ STATIC mp_obj_t keypad_keymatrix_make_new(const mp_obj_type_t *type, size_t n_ar
 
     common_hal_keypad_keymatrix_construct(self, num_row_pins, row_pins_array, num_column_pins, column_pins_array, args[ARG_columns_to_anodes].u_bool, interval, max_events);
     return MP_OBJ_FROM_PTR(self);
+    #else
+    mp_raise_NotImplementedError_varg(translate("%q"), MP_QSTR_KeyMatrix);
+
+    #endif
 }
 
+#if CIRCUITPY_KEYPAD_KEYMATRIX
 //|     def deinit(self) -> None:
 //|         """Stop scanning and release the pins."""
 //|         ...
@@ -228,9 +234,13 @@ STATIC const mp_rom_map_elem_t keypad_keymatrix_locals_dict_table[] = {
 
 STATIC MP_DEFINE_CONST_DICT(keypad_keymatrix_locals_dict, keypad_keymatrix_locals_dict_table);
 
+#endif
+
 const mp_obj_type_t keypad_keymatrix_type = {
     { &mp_type_type },
     .name = MP_QSTR_KeyMatrix,
     .make_new = keypad_keymatrix_make_new,
+    #if CIRCUITPY_KEYPAD_KEYMATRIX
     .locals_dict = (mp_obj_t)&keypad_keymatrix_locals_dict,
+    #endif
 };
diff --git a/shared-bindings/keypad/Keys.c b/shared-bindings/keypad/Keys.c
index 10519958c7..2481fedc6b 100644
--- a/shared-bindings/keypad/Keys.c
+++ b/shared-bindings/keypad/Keys.c
@@ -73,6 +73,7 @@
 //|         ...
 
 STATIC mp_obj_t keypad_keys_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
+    #if CIRCUITPY_KEYPAD_KEYS
     keypad_keys_obj_t *self = m_new_obj(keypad_keys_obj_t);
     self->base.type = &keypad_keys_type;
     enum { ARG_pins, ARG_value_when_pressed, ARG_pull, ARG_interval, ARG_max_events };
@@ -106,8 +107,13 @@ STATIC mp_obj_t keypad_keys_make_new(const mp_obj_type_t *type, size_t n_args, s
     common_hal_keypad_keys_construct(self, num_pins, pins_array, value_when_pressed, args[ARG_pull].u_bool, interval, max_events);
 
     return MP_OBJ_FROM_PTR(self);
+    #else
+    mp_raise_NotImplementedError_varg(translate("%q"), MP_QSTR_Keys);
+
+    #endif
 }
 
+#if CIRCUITPY_KEYPAD_KEYS
 //|     def deinit(self) -> None:
 //|         """Stop scanning and release the pins."""
 //|         ...
@@ -162,10 +168,13 @@ STATIC const mp_rom_map_elem_t keypad_keys_locals_dict_table[] = {
 };
 
 STATIC MP_DEFINE_CONST_DICT(keypad_keys_locals_dict, keypad_keys_locals_dict_table);
+#endif
 
 const mp_obj_type_t keypad_keys_type = {
     { &mp_type_type },
     .name = MP_QSTR_Keys,
     .make_new = keypad_keys_make_new,
+    #if CIRCUITPY_KEYPAD_KEYS
     .locals_dict = (mp_obj_t)&keypad_keys_locals_dict,
+    #endif
 };
diff --git a/shared-bindings/keypad/ShiftRegisterKeys.c b/shared-bindings/keypad/ShiftRegisterKeys.c
index 9113be33d2..1fcf517ac3 100644
--- a/shared-bindings/keypad/ShiftRegisterKeys.c
+++ b/shared-bindings/keypad/ShiftRegisterKeys.c
@@ -82,6 +82,7 @@
 //|         ...
 
 STATIC mp_obj_t keypad_shiftregisterkeys_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
+    #if CIRCUITPY_KEYPAD_SHIFTREGISTERKEYS
     keypad_shiftregisterkeys_obj_t *self = m_new_obj(keypad_shiftregisterkeys_obj_t);
     self->base.type = &keypad_shiftregisterkeys_type;
     enum { ARG_clock, ARG_data, ARG_latch, ARG_value_to_latch, ARG_key_count, ARG_value_when_pressed, ARG_interval, ARG_max_events };
@@ -113,8 +114,12 @@ STATIC mp_obj_t keypad_shiftregisterkeys_make_new(const mp_obj_type_t *type, siz
         self, clock, data, latch, value_to_latch, key_count, value_when_pressed, interval, max_events);
 
     return MP_OBJ_FROM_PTR(self);
+    #else
+    mp_raise_NotImplementedError_varg(translate("%q"), MP_QSTR_ShiftRegisterKeys);
+    #endif
 }
 
+#if CIRCUITPY_KEYPAD_SHIFTREGISTERKEYS
 //|     def deinit(self) -> None:
 //|         """Stop scanning and release the pins."""
 //|         ...
@@ -169,10 +174,13 @@ STATIC const mp_rom_map_elem_t keypad_shiftregisterkeys_locals_dict_table[] = {
 };
 
 STATIC MP_DEFINE_CONST_DICT(keypad_shiftregisterkeys_locals_dict, keypad_shiftregisterkeys_locals_dict_table);
+#endif
 
 const mp_obj_type_t keypad_shiftregisterkeys_type = {
     { &mp_type_type },
     .name = MP_QSTR_ShiftRegisterKeys,
     .make_new = keypad_shiftregisterkeys_make_new,
+    #if CIRCUITPY_KEYPAD_SHIFTREGISTERKEYS
     .locals_dict = (mp_obj_t)&keypad_shiftregisterkeys_locals_dict,
+    #endif
 };
diff --git a/shared-bindings/synthio/MidiTrack.c b/shared-bindings/synthio/MidiTrack.c
index b987337eaa..20a203ce9c 100644
--- a/shared-bindings/synthio/MidiTrack.c
+++ b/shared-bindings/synthio/MidiTrack.c
@@ -32,13 +32,19 @@
 #include "py/runtime.h"
 #include "shared-bindings/util.h"
 #include "shared-bindings/synthio/MidiTrack.h"
+#include "shared-bindings/synthio/__init__.h"
 #include "supervisor/shared/translate/translate.h"
 
 //| class MidiTrack:
-//|     """Simple square-wave MIDI synth"""
+//|     """Simple MIDI synth"""
 //|
 //|     def __init__(
-//|         self, buffer: ReadableBuffer, tempo: int, *, sample_rate: int = 11025
+//|         self,
+//|         buffer: ReadableBuffer,
+//|         tempo: int,
+//|         *,
+//|         sample_rate: int = 11025,
+//|         waveform: ReadableBuffer = None
 //|     ) -> None:
 //|         """Create a MidiTrack from the given stream of MIDI events. Only "Note On" and "Note Off" events
 //|         are supported; channel numbers and key velocities are ignored. Up to two notes may be on at the
@@ -47,6 +53,7 @@
 //|         :param ~circuitpython_typing.ReadableBuffer buffer: Stream of MIDI events, as stored in a MIDI file track chunk
 //|         :param int tempo: Tempo of the streamed events, in MIDI ticks per second
 //|         :param int sample_rate: The desired playback sample rate; higher sample rate requires more memory
+//|         :param ReadableBuffer waveform: A single-cycle waveform. Default is a 50% duty cycle square wave. If specified, must be a ReadableBuffer of type 'h' (signed 16 bit)
 //|
 //|         Simple melody::
 //|
@@ -65,11 +72,12 @@
 //|           print("stopped")"""
 //|         ...
 STATIC mp_obj_t synthio_miditrack_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
-    enum { ARG_buffer, ARG_tempo, ARG_sample_rate };
+    enum { ARG_buffer, ARG_tempo, ARG_sample_rate, ARG_waveform };
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_buffer, MP_ARG_OBJ | MP_ARG_REQUIRED },
         { MP_QSTR_tempo, MP_ARG_INT | MP_ARG_REQUIRED },
         { MP_QSTR_sample_rate, MP_ARG_INT | MP_ARG_KW_ONLY, {.u_int = 11025} },
+        { MP_QSTR_waveform, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = mp_const_none } },
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all_kw_array(n_args, n_kw, all_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
@@ -77,13 +85,18 @@ STATIC mp_obj_t synthio_miditrack_make_new(const mp_obj_type_t *type, size_t n_a
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(args[ARG_buffer].u_obj, &bufinfo, MP_BUFFER_READ);
 
+    mp_buffer_info_t bufinfo_waveform;
+    synthio_synth_parse_waveform(&bufinfo_waveform, args[ARG_waveform].u_obj);
+
     synthio_miditrack_obj_t *self = m_new_obj(synthio_miditrack_obj_t);
     self->base.type = &synthio_miditrack_type;
 
     common_hal_synthio_miditrack_construct(self,
         (uint8_t *)bufinfo.buf, bufinfo.len,
         args[ARG_tempo].u_int,
-        args[ARG_sample_rate].u_int);
+        args[ARG_sample_rate].u_int,
+        bufinfo_waveform.buf,
+        bufinfo_waveform.len / 2);
 
     return MP_OBJ_FROM_PTR(self);
 }
diff --git a/shared-bindings/synthio/MidiTrack.h b/shared-bindings/synthio/MidiTrack.h
index d44d4c3bb7..90ddab8728 100644
--- a/shared-bindings/synthio/MidiTrack.h
+++ b/shared-bindings/synthio/MidiTrack.h
@@ -32,7 +32,7 @@
 extern const mp_obj_type_t synthio_miditrack_type;
 
 void common_hal_synthio_miditrack_construct(synthio_miditrack_obj_t *self,
-    const uint8_t *buffer, uint32_t len, uint32_t tempo, uint32_t sample_rate);
+    const uint8_t *buffer, uint32_t len, uint32_t tempo, uint32_t sample_rate, const int16_t *waveform, uint16_t waveform_len);
 
 void common_hal_synthio_miditrack_deinit(synthio_miditrack_obj_t *self);
 bool common_hal_synthio_miditrack_deinited(synthio_miditrack_obj_t *self);
diff --git a/shared-bindings/synthio/Synthesizer.c b/shared-bindings/synthio/Synthesizer.c
new file mode 100644
index 0000000000..2ad5cbcd42
--- /dev/null
+++ b/shared-bindings/synthio/Synthesizer.c
@@ -0,0 +1,211 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 Artyom Skrobov
+ * Copyright (c) 2023 Jeff Epler for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <stdint.h>
+
+#include "shared/runtime/context_manager_helpers.h"
+#include "py/binary.h"
+#include "py/objproperty.h"
+#include "py/runtime.h"
+#include "shared-bindings/util.h"
+#include "shared-bindings/synthio/Synthesizer.h"
+#include "shared-bindings/synthio/__init__.h"
+#include "supervisor/shared/translate/translate.h"
+
+//| class Synth:
+//|     def __init__(self, *, sample_rate: int = 11025, waveform: ReadableBuffer = None) -> None:
+//|         """Create a synthesizer object."""
+STATIC mp_obj_t synthio_synthesizer_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *all_args) {
+    enum { ARG_sample_rate, ARG_waveform };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_sample_rate, MP_ARG_INT | MP_ARG_KW_ONLY, {.u_int = 11025} },
+        { MP_QSTR_waveform, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = mp_const_none } },
+    };
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all_kw_array(n_args, n_kw, all_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    mp_buffer_info_t bufinfo_waveform;
+    synthio_synth_parse_waveform(&bufinfo_waveform, args[ARG_waveform].u_obj);
+
+    synthio_synthesizer_obj_t *self = m_new_obj(synthio_synthesizer_obj_t);
+    self->base.type = &synthio_synthesizer_type;
+
+    common_hal_synthio_synthesizer_construct(self,
+        args[ARG_sample_rate].u_int,
+        bufinfo_waveform.buf,
+        bufinfo_waveform.len / 2);
+
+    return MP_OBJ_FROM_PTR(self);
+}
+
+STATIC void check_for_deinit(synthio_synthesizer_obj_t *self) {
+    if (common_hal_synthio_synthesizer_deinited(self)) {
+        raise_deinited_error();
+    }
+}
+
+//|     def press(self, /, press: Sequence[int] = ()) -> None:
+//|         """Turn some notes on. Notes use MIDI numbering, with 60 being middle C."""
+STATIC mp_obj_t synthio_synthesizer_press(mp_obj_t self_in, mp_obj_t press) {
+    synthio_synthesizer_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    check_for_deinit(self);
+    common_hal_synthio_synthesizer_press(self, press);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(synthio_synthesizer_press_obj, synthio_synthesizer_press);
+//
+//|     def release_then_press(
+//|         self, release: Sequence[int] = (), press: Sequence[int] = ()
+//|     ) -> None:
+//|         """Turn some notes on and/or off. Notes use MIDI numbering, with 60 being middle C."""
+STATIC mp_obj_t synthio_synthesizer_release_then_press(mp_uint_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_release, ARG_press };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_release, MP_ARG_OBJ, {.u_obj = mp_const_empty_tuple } },
+        { MP_QSTR_press, MP_ARG_OBJ, {.u_obj = mp_const_empty_tuple } },
+    };
+
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    synthio_synthesizer_obj_t *self = MP_OBJ_TO_PTR(pos_args[0]);
+    check_for_deinit(self);
+    common_hal_synthio_synthesizer_release(self, args[ARG_release].u_obj);
+    common_hal_synthio_synthesizer_press(self, args[ARG_press].u_obj);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_KW(synthio_synthesizer_release_then_press_obj, 1, synthio_synthesizer_release_then_press);
+
+//
+//|     def release_all_then_press(self, /, press: Sequence[int]) -> None:
+//|         """Turn any currently-playing notes off, then turn on the given notes"""
+STATIC mp_obj_t synthio_synthesizer_release_all_then_press(mp_obj_t self_in, mp_obj_t press) {
+    synthio_synthesizer_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    check_for_deinit(self);
+    common_hal_synthio_synthesizer_release_all(self);
+    common_hal_synthio_synthesizer_press(self, press);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(synthio_synthesizer_release_all_then_press_obj, synthio_synthesizer_release_all_then_press);
+
+//
+//|     def release_all(self) -> None:
+//|         """Turn any currently-playing notes off"""
+STATIC mp_obj_t synthio_synthesizer_release_all(mp_obj_t self_in) {
+    synthio_synthesizer_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    check_for_deinit(self);
+    common_hal_synthio_synthesizer_release_all(self);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(synthio_synthesizer_release_all_obj, synthio_synthesizer_release_all);
+
+//|     def deinit(self) -> None:
+//|         """Deinitialises the object and releases any memory resources for reuse."""
+//|         ...
+STATIC mp_obj_t synthio_synthesizer_deinit(mp_obj_t self_in) {
+    synthio_synthesizer_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    common_hal_synthio_synthesizer_deinit(self);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(synthio_synthesizer_deinit_obj, synthio_synthesizer_deinit);
+
+//|     def __enter__(self) -> MidiTrack:
+//|         """No-op used by Context Managers."""
+//|         ...
+//  Provided by context manager helper.
+//|
+//|     def __exit__(self) -> None:
+//|         """Automatically deinitializes the hardware when exiting a context. See
+//|         :ref:`lifetime-and-contextmanagers` for more info."""
+//|         ...
+STATIC mp_obj_t synthio_synthesizer_obj___exit__(size_t n_args, const mp_obj_t *args) {
+    (void)n_args;
+    common_hal_synthio_synthesizer_deinit(args[0]);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(synthio_synthesizer___exit___obj, 4, 4, synthio_synthesizer_obj___exit__);
+//|     sample_rate: int
+//|     """32 bit value that tells how quickly samples are played in Hertz (cycles per second)."""
+STATIC mp_obj_t synthio_synthesizer_obj_get_sample_rate(mp_obj_t self_in) {
+    synthio_synthesizer_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    check_for_deinit(self);
+    return MP_OBJ_NEW_SMALL_INT(common_hal_synthio_synthesizer_get_sample_rate(self));
+}
+MP_DEFINE_CONST_FUN_OBJ_1(synthio_synthesizer_get_sample_rate_obj, synthio_synthesizer_obj_get_sample_rate);
+
+MP_PROPERTY_GETTER(synthio_synthesizer_sample_rate_obj,
+    (mp_obj_t)&synthio_synthesizer_get_sample_rate_obj);
+
+//|     pressed: Tuple[int]
+//|     """A sequence of the currently pressed notes (read-only property)"""
+//|
+STATIC mp_obj_t synthio_synthesizer_obj_get_pressed(mp_obj_t self_in) {
+    synthio_synthesizer_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    check_for_deinit(self);
+    return common_hal_synthio_synthesizer_get_pressed_notes(self);
+}
+MP_DEFINE_CONST_FUN_OBJ_1(synthio_synthesizer_get_pressed_obj, synthio_synthesizer_obj_get_pressed);
+
+MP_PROPERTY_GETTER(synthio_synthesizer_pressed_obj,
+    (mp_obj_t)&synthio_synthesizer_get_pressed_obj);
+
+STATIC const mp_rom_map_elem_t synthio_synthesizer_locals_dict_table[] = {
+    // Methods
+    { MP_ROM_QSTR(MP_QSTR_press), MP_ROM_PTR(&synthio_synthesizer_press_obj) },
+    { MP_ROM_QSTR(MP_QSTR_release_all), MP_ROM_PTR(&synthio_synthesizer_release_all_obj) },
+    { MP_ROM_QSTR(MP_QSTR_release_then_press), MP_ROM_PTR(&synthio_synthesizer_release_then_press_obj) },
+    { MP_ROM_QSTR(MP_QSTR_release_all_then_press), MP_ROM_PTR(&synthio_synthesizer_release_all_then_press_obj) },
+    { MP_ROM_QSTR(MP_QSTR_deinit), MP_ROM_PTR(&synthio_synthesizer_deinit_obj) },
+    { MP_ROM_QSTR(MP_QSTR___enter__), MP_ROM_PTR(&default___enter___obj) },
+    { MP_ROM_QSTR(MP_QSTR___exit__), MP_ROM_PTR(&synthio_synthesizer___exit___obj) },
+
+    // Properties
+    { MP_ROM_QSTR(MP_QSTR_sample_rate), MP_ROM_PTR(&synthio_synthesizer_sample_rate_obj) },
+    { MP_ROM_QSTR(MP_QSTR_pressed), MP_ROM_PTR(&synthio_synthesizer_pressed_obj) },
+};
+STATIC MP_DEFINE_CONST_DICT(synthio_synthesizer_locals_dict, synthio_synthesizer_locals_dict_table);
+
+STATIC const audiosample_p_t synthio_synthesizer_proto = {
+    MP_PROTO_IMPLEMENT(MP_QSTR_protocol_audiosample)
+    .sample_rate = (audiosample_sample_rate_fun)common_hal_synthio_synthesizer_get_sample_rate,
+    .bits_per_sample = (audiosample_bits_per_sample_fun)common_hal_synthio_synthesizer_get_bits_per_sample,
+    .channel_count = (audiosample_channel_count_fun)common_hal_synthio_synthesizer_get_channel_count,
+    .reset_buffer = (audiosample_reset_buffer_fun)synthio_synthesizer_reset_buffer,
+    .get_buffer = (audiosample_get_buffer_fun)synthio_synthesizer_get_buffer,
+    .get_buffer_structure = (audiosample_get_buffer_structure_fun)synthio_synthesizer_get_buffer_structure,
+};
+
+const mp_obj_type_t synthio_synthesizer_type = {
+    { &mp_type_type },
+    .name = MP_QSTR_Synthesizer,
+    .flags = MP_TYPE_FLAG_EXTENDED,
+    .make_new = synthio_synthesizer_make_new,
+    .locals_dict = (mp_obj_dict_t *)&synthio_synthesizer_locals_dict,
+    MP_TYPE_EXTENDED_FIELDS(
+        .protocol = &synthio_synthesizer_proto,
+        ),
+};
diff --git a/shared-bindings/synthio/Synthesizer.h b/shared-bindings/synthio/Synthesizer.h
new file mode 100644
index 0000000000..92e75a1c23
--- /dev/null
+++ b/shared-bindings/synthio/Synthesizer.h
@@ -0,0 +1,45 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 Artyom Skrobov
+ * Copyright (c) 2023 Jeff Epler for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#pragma once
+
+#include "shared-module/synthio/Synthesizer.h"
+
+extern const mp_obj_type_t synthio_synthesizer_type;
+
+void common_hal_synthio_synthesizer_construct(synthio_synthesizer_obj_t *self,
+    uint32_t sample_rate, const int16_t *waveform, uint16_t waveform_len);
+
+void common_hal_synthio_synthesizer_deinit(synthio_synthesizer_obj_t *self);
+bool common_hal_synthio_synthesizer_deinited(synthio_synthesizer_obj_t *self);
+uint32_t common_hal_synthio_synthesizer_get_sample_rate(synthio_synthesizer_obj_t *self);
+uint8_t common_hal_synthio_synthesizer_get_bits_per_sample(synthio_synthesizer_obj_t *self);
+uint8_t common_hal_synthio_synthesizer_get_channel_count(synthio_synthesizer_obj_t *self);
+void common_hal_synthio_synthesizer_release(synthio_synthesizer_obj_t *self, mp_obj_t to_release);
+void common_hal_synthio_synthesizer_press(synthio_synthesizer_obj_t *self, mp_obj_t to_press);
+void common_hal_synthio_synthesizer_release_all(synthio_synthesizer_obj_t *self);
+mp_obj_t common_hal_synthio_synthesizer_get_pressed_notes(synthio_synthesizer_obj_t *self);
diff --git a/shared-bindings/synthio/__init__.c b/shared-bindings/synthio/__init__.c
index 106a073535..3c50377ff8 100644
--- a/shared-bindings/synthio/__init__.c
+++ b/shared-bindings/synthio/__init__.c
@@ -30,9 +30,11 @@
 #include "py/obj.h"
 #include "py/runtime.h"
 #include "extmod/vfs_fat.h"
+#include "extmod/vfs_posix.h"
 
 #include "shared-bindings/synthio/__init__.h"
 #include "shared-bindings/synthio/MidiTrack.h"
+#include "shared-bindings/synthio/Synthesizer.h"
 
 //| """Support for MIDI synthesis"""
 //|
@@ -42,6 +44,7 @@
 //|
 //|     :param typing.BinaryIO file: Already opened MIDI file
 //|     :param int sample_rate: The desired playback sample rate; higher sample rate requires more memory
+//|     :param ReadableBuffer waveform: A single-cycle waveform. Default is a 50% duty cycle square wave. If specified, must be a ReadableBuffer of type 'h' (signed 16 bit)
 //|
 //|
 //|     Playing a MIDI file from flash::
@@ -62,10 +65,11 @@
 //|     ...
 //|
 STATIC mp_obj_t synthio_from_file(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
-    enum { ARG_file, ARG_sample_rate };
+    enum { ARG_file, ARG_sample_rate, ARG_waveform };
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED },
         { MP_QSTR_sample_rate, MP_ARG_INT | MP_ARG_KW_ONLY, {.u_int = 11025} },
+        { MP_QSTR_waveform, MP_ARG_OBJ | MP_ARG_KW_ONLY, {.u_obj = mp_const_none } },
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
@@ -74,6 +78,10 @@ STATIC mp_obj_t synthio_from_file(size_t n_args, const mp_obj_t *pos_args, mp_ma
     }
     pyb_file_obj_t *file = MP_OBJ_TO_PTR(args[ARG_file].u_obj);
 
+
+    mp_buffer_info_t bufinfo_waveform;
+    synthio_synth_parse_waveform(&bufinfo_waveform, args[ARG_waveform].u_obj);
+
     uint8_t chunk_header[14];
     f_rewind(&file->fp);
     UINT bytes_read;
@@ -113,9 +121,13 @@ STATIC mp_obj_t synthio_from_file(size_t n_args, const mp_obj_t *pos_args, mp_ma
     result->base.type = &synthio_miditrack_type;
 
     common_hal_synthio_miditrack_construct(result, buffer, track_size,
-        tempo, args[ARG_sample_rate].u_int);
+        tempo, args[ARG_sample_rate].u_int, bufinfo_waveform.buf, bufinfo_waveform.len / 2);
 
+    #if MICROPY_MALLOC_USES_ALLOCATED_SIZE
+    m_free(buffer, track_size);
+    #else
     m_free(buffer);
+    #endif
 
     return MP_OBJ_FROM_PTR(result);
 }
@@ -125,6 +137,7 @@ MP_DEFINE_CONST_FUN_OBJ_KW(synthio_from_file_obj, 1, synthio_from_file);
 STATIC const mp_rom_map_elem_t synthio_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_synthio) },
     { MP_ROM_QSTR(MP_QSTR_MidiTrack), MP_ROM_PTR(&synthio_miditrack_type) },
+    { MP_ROM_QSTR(MP_QSTR_Synthesizer), MP_ROM_PTR(&synthio_synthesizer_type) },
     { MP_ROM_QSTR(MP_QSTR_from_file), MP_ROM_PTR(&synthio_from_file_obj) },
 };
 
diff --git a/shared-bindings/synthio/__init__.h b/shared-bindings/synthio/__init__.h
index 14af1a5805..3b7d47db28 100644
--- a/shared-bindings/synthio/__init__.h
+++ b/shared-bindings/synthio/__init__.h
@@ -24,11 +24,6 @@
  * THE SOFTWARE.
  */
 
-#ifndef MICROPY_INCLUDED_SHARED_BINDINGS_SYNTHIO___INIT___H
-#define MICROPY_INCLUDED_SHARED_BINDINGS_SYNTHIO___INIT___H
+#pragma once
 
-#include "py/obj.h"
-
-// Nothing now.
-
-#endif  // MICROPY_INCLUDED_SHARED_BINDINGS_SYNTHIO___INIT___H
+extern int16_t shared_bindings_synthio_square_wave[];
diff --git a/shared-module/audiomixer/Mixer.c b/shared-module/audiomixer/Mixer.c
index 1c5de4d934..397a837133 100644
--- a/shared-module/audiomixer/Mixer.c
+++ b/shared-module/audiomixer/Mixer.c
@@ -33,7 +33,10 @@
 
 #include "py/runtime.h"
 #include "shared-module/audiocore/__init__.h"
-#include "shared-module/audiocore/RawSample.h"
+
+#if defined(__arm__) && __arm__
+#include "cmsis_compiler.h"
+#endif
 
 void common_hal_audiomixer_mixer_construct(audiomixer_mixer_obj_t *self,
     uint8_t voice_count,
@@ -140,7 +143,7 @@ static inline uint32_t mult16signed(uint32_t val, int32_t mul) {
     float mod_mul = (float)mul / (float)((1 << 15) - 1);
     for (int8_t i = 0; i < 2; i++) {
         int16_t ai = (val >> (sizeof(uint16_t) * 8 * i));
-        int32_t intermediate = ai * mod_mul;
+        int32_t intermediate = (int32_t)(ai * mod_mul);
         if (intermediate > SHRT_MAX) {
             intermediate = SHRT_MAX;
         } else if (intermediate < SHRT_MIN) {
diff --git a/shared-module/audiomixer/MixerVoice.c b/shared-module/audiomixer/MixerVoice.c
index bb58b0c111..f4d2a6514e 100644
--- a/shared-module/audiomixer/MixerVoice.c
+++ b/shared-module/audiomixer/MixerVoice.c
@@ -42,12 +42,12 @@ void common_hal_audiomixer_mixervoice_set_parent(audiomixer_mixervoice_obj_t *se
     self->parent = parent;
 }
 
-float common_hal_audiomixer_mixervoice_get_level(audiomixer_mixervoice_obj_t *self) {
-    return (float)self->level / (1 << 15);
+mp_float_t common_hal_audiomixer_mixervoice_get_level(audiomixer_mixervoice_obj_t *self) {
+    return (mp_float_t)self->level / (1 << 15);
 }
 
-void common_hal_audiomixer_mixervoice_set_level(audiomixer_mixervoice_obj_t *self, float level) {
-    self->level = level * (1 << 15);
+void common_hal_audiomixer_mixervoice_set_level(audiomixer_mixervoice_obj_t *self, mp_float_t level) {
+    self->level = (uint16_t)(level * (1 << 15));
 }
 
 void common_hal_audiomixer_mixervoice_play(audiomixer_mixervoice_obj_t *self, mp_obj_t sample, bool loop) {
diff --git a/shared-module/synthio/MidiTrack.c b/shared-module/synthio/MidiTrack.c
index f02747d734..f8b39c29e3 100644
--- a/shared-module/synthio/MidiTrack.c
+++ b/shared-module/synthio/MidiTrack.c
@@ -27,10 +27,6 @@
 #include "py/runtime.h"
 #include "shared-bindings/synthio/MidiTrack.h"
 
-#define LOUDNESS 0x4000  // 0.5
-#define BITS_PER_SAMPLE 16
-#define BYTES_PER_SAMPLE (BITS_PER_SAMPLE / 8)
-#define SILENCE 0x80
 
 STATIC NORETURN void raise_midi_stream_error(uint32_t pos) {
     mp_raise_ValueError_varg(translate("Error in MIDI stream at position %d"), pos);
@@ -47,36 +43,42 @@ STATIC uint8_t parse_note(const uint8_t *buffer, uint32_t len, uint32_t *pos) {
     return note;
 }
 
-STATIC void terminate_span(synthio_miditrack_obj_t *self, uint16_t *dur, uint16_t *max_dur) {
+STATIC void terminate_span(synthio_miditrack_obj_t *self, uint16_t *dur) {
     if (*dur) {
         self->track[self->total_spans - 1].dur = *dur;
-        if (*dur > *max_dur) {
-            *max_dur = *dur;
-        }
         *dur = 0;
     } else {
         self->total_spans--;
     }
 }
 
-STATIC void add_span(synthio_miditrack_obj_t *self, uint8_t note1, uint8_t note2) {
-    synthio_midi_span_t span = { 0, {note1, note2} };
-    self->track = m_realloc(self->track,
-        (self->total_spans + 1) * sizeof(synthio_midi_span_t));
-    self->track[self->total_spans++] = span;
+STATIC void add_span(synthio_miditrack_obj_t *self, const synthio_midi_span_t *span) {
+    self->track = m_renew(synthio_midi_span_t, self->track, self->total_spans, self->total_spans + 1);
+    self->track[self->total_spans++] = *span;
+}
+
+STATIC void change_span_note(synthio_miditrack_obj_t *self, uint8_t old_note, uint8_t new_note, uint16_t *dur) {
+    synthio_midi_span_t span = self->track[self->total_spans - 1];
+    if (synthio_span_change_note(&span, old_note, new_note)) {
+        terminate_span(self, dur);
+        add_span(self, &span);
+        *dur = 0;
+    }
 }
 
 void common_hal_synthio_miditrack_construct(synthio_miditrack_obj_t *self,
-    const uint8_t *buffer, uint32_t len, uint32_t tempo, uint32_t sample_rate) {
+    const uint8_t *buffer, uint32_t len, uint32_t tempo, uint32_t sample_rate,
+    const int16_t *waveform, uint16_t waveform_length) {
 
-    synthio_midi_span_t initial = { 0, {SILENCE, SILENCE} };
-    self->sample_rate = sample_rate;
+    self->synth.sample_rate = sample_rate;
     self->track = m_malloc(sizeof(synthio_midi_span_t), false);
+    synthio_span_init(self->track);
     self->next_span = 0;
     self->total_spans = 1;
-    *self->track = initial;
+    self->synth.waveform = waveform;
+    self->synth.waveform_length = waveform_length;
 
-    uint16_t dur = 0, max_dur = 0;
+    uint16_t dur = 0;
     uint32_t pos = 0;
     while (pos < len) {
         uint8_t c;
@@ -91,37 +93,19 @@ void common_hal_synthio_miditrack_construct(synthio_miditrack_obj_t *self,
             raise_midi_stream_error(pos);
         }
 
+        // dur is carried over here so that if a note on/off message doesn't actually produce a change, the
+        // underlying "span" is extended. Otherwise, it is zeroed out in the call to `terminate_span`.
         dur += delta * sample_rate / tempo;
 
         switch (buffer[pos++] >> 4) {
             case 8: { // Note Off
                 uint8_t note = parse_note(buffer, len, &pos);
-
-                // Ignore if not a note which is playing
-                synthio_midi_span_t last_span = self->track[self->total_spans - 1];
-                if (last_span.note[0] == note || last_span.note[1] == note) {
-                    terminate_span(self, &dur, &max_dur);
-                    if (last_span.note[0] == note) {
-                        add_span(self, last_span.note[1], SILENCE);
-                    } else {
-                        add_span(self, last_span.note[0], SILENCE);
-                    }
-                }
+                change_span_note(self, note, SYNTHIO_SILENCE, &dur);
                 break;
             }
             case 9: { // Note On
                 uint8_t note = parse_note(buffer, len, &pos);
-
-                // Ignore if two notes are already playing
-                synthio_midi_span_t last_span = self->track[self->total_spans - 1];
-                if (last_span.note[1] == SILENCE) {
-                    terminate_span(self, &dur, &max_dur);
-                    if (last_span.note[0] == SILENCE) {
-                        add_span(self, note, SILENCE);
-                    } else {
-                        add_span(self, last_span.note[0], note);
-                    }
-                }
+                change_span_note(self, SYNTHIO_SILENCE, note, &dur);
                 break;
             }
             case 10:
@@ -142,27 +126,29 @@ void common_hal_synthio_miditrack_construct(synthio_miditrack_obj_t *self,
                 raise_midi_stream_error(pos);
         }
     }
-    terminate_span(self, &dur, &max_dur);
+    terminate_span(self, &dur);
 
-    self->buffer_length = max_dur * BYTES_PER_SAMPLE;
-    self->buffer = m_malloc(self->buffer_length, false);
+    uint16_t max_dur = 0;
+    for (int i = 0; i < self->total_spans; i++) {
+        max_dur = MAX(self->track[i].dur, max_dur);
+    }
+    synthio_synth_init(&self->synth, max_dur);
 }
 
 void common_hal_synthio_miditrack_deinit(synthio_miditrack_obj_t *self) {
-    m_free(self->buffer);
-    self->buffer = NULL;
-    m_free(self->track);
+    synthio_synth_deinit(&self->synth);
+    m_del(synthio_midi_span_t, self->track, self->total_spans + 1);
     self->track = NULL;
 }
 bool common_hal_synthio_miditrack_deinited(synthio_miditrack_obj_t *self) {
-    return self->buffer == NULL;
+    return synthio_synth_deinited(&self->synth);
 }
 
 uint32_t common_hal_synthio_miditrack_get_sample_rate(synthio_miditrack_obj_t *self) {
-    return self->sample_rate;
+    return self->synth.sample_rate;
 }
 uint8_t common_hal_synthio_miditrack_get_bits_per_sample(synthio_miditrack_obj_t *self) {
-    return BITS_PER_SAMPLE;
+    return SYNTHIO_BITS_PER_SAMPLE;
 }
 uint8_t common_hal_synthio_miditrack_get_channel_count(synthio_miditrack_obj_t *self) {
     return 1;
@@ -170,47 +156,29 @@ uint8_t common_hal_synthio_miditrack_get_channel_count(synthio_miditrack_obj_t *
 
 void synthio_miditrack_reset_buffer(synthio_miditrack_obj_t *self,
     bool single_channel_output, uint8_t channel) {
-
+    synthio_synth_reset_buffer(&self->synth, single_channel_output, channel);
+    self->synth.span.dur = 0;
     self->next_span = 0;
 }
 
-STATIC const uint16_t notes[] = {8372, 8870, 9397, 9956, 10548, 11175, 11840,
-                                 12544, 13290, 14080, 14917, 15804}; // 9th octave
-
 audioio_get_buffer_result_t synthio_miditrack_get_buffer(synthio_miditrack_obj_t *self,
     bool single_channel_output, uint8_t channel, uint8_t **buffer, uint32_t *buffer_length) {
 
-    if (self->next_span >= self->total_spans) {
-        *buffer_length = 0;
-        return GET_BUFFER_DONE;
+    if (self->synth.span.dur == 0) {
+        if (self->next_span >= self->total_spans) {
+            *buffer_length = 0;
+            return GET_BUFFER_DONE;
+        }
+        self->synth.span = self->track[self->next_span++];
     }
 
-    synthio_midi_span_t span = self->track[self->next_span++];
-    *buffer_length = span.dur * BYTES_PER_SAMPLE;
-    uint8_t octave1 = span.note[0] / 12; // 0..10
-    uint8_t octave2 = span.note[1] / 12; // 0..10
-    int32_t base_freq1 = notes[span.note[0] % 12];
-    int32_t base_freq2 = notes[span.note[1] % 12];
-    int32_t sample_rate = self->sample_rate;
+    synthio_synth_synthesize(&self->synth, buffer, buffer_length, single_channel_output ? 0 : channel);
 
-    for (uint16_t i = 0; i < span.dur; i++) {
-        int16_t semiperiod1 = span.note[0] == SILENCE ? 0 :
-            ((base_freq1 * i * 2) / sample_rate) >> (10 - octave1);
-        int16_t semiperiod2 = span.note[1] == SILENCE ? semiperiod1 :
-            ((base_freq2 * i * 2) / sample_rate) >> (10 - octave2);
-        self->buffer[i] = ((semiperiod1 % 2 + semiperiod2 % 2) - 1) * LOUDNESS;
-    }
-    *buffer = (uint8_t *)self->buffer;
-
-    return self->next_span >= self->total_spans ?
+    return (self->synth.span.dur == 0 && self->next_span >= self->total_spans) ?
            GET_BUFFER_DONE : GET_BUFFER_MORE_DATA;
 }
 
 void synthio_miditrack_get_buffer_structure(synthio_miditrack_obj_t *self, bool single_channel_output,
     bool *single_buffer, bool *samples_signed, uint32_t *max_buffer_length, uint8_t *spacing) {
-
-    *single_buffer = true;
-    *samples_signed = true;
-    *max_buffer_length = self->buffer_length;
-    *spacing = 1;
+    return synthio_synth_get_buffer_structure(&self->synth, single_channel_output, single_buffer, samples_signed, max_buffer_length, spacing);
 }
diff --git a/shared-module/synthio/MidiTrack.h b/shared-module/synthio/MidiTrack.h
index 0af174ebc1..e301ef355f 100644
--- a/shared-module/synthio/MidiTrack.h
+++ b/shared-module/synthio/MidiTrack.h
@@ -31,19 +31,12 @@
 
 #include "shared-module/synthio/__init__.h"
 
-typedef struct {
-    uint16_t dur;
-    uint8_t note[2];
-} synthio_midi_span_t;
-
 typedef struct {
     mp_obj_base_t base;
-    uint32_t sample_rate;
-    uint16_t *buffer;
-    uint16_t buffer_length;
-    synthio_midi_span_t *track;
+    synthio_synth_t synth;
     uint16_t next_span;
     uint16_t total_spans;
+    synthio_midi_span_t *track;
 } synthio_miditrack_obj_t;
 
 
diff --git a/shared-module/synthio/Synthesizer.c b/shared-module/synthio/Synthesizer.c
new file mode 100644
index 0000000000..25c91ecbe0
--- /dev/null
+++ b/shared-module/synthio/Synthesizer.c
@@ -0,0 +1,105 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 Artyom Skrobov
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "py/runtime.h"
+#include "shared-bindings/synthio/Synthesizer.h"
+
+
+
+void common_hal_synthio_synthesizer_construct(synthio_synthesizer_obj_t *self,
+    uint32_t sample_rate, const int16_t *waveform, uint16_t waveform_length) {
+
+    self->synth.sample_rate = sample_rate;
+    self->synth.waveform = waveform;
+    self->synth.waveform_length = waveform_length;
+    synthio_synth_init(&self->synth, SYNTHIO_MAX_DUR);
+    common_hal_synthio_synthesizer_release_all(self);
+}
+
+void common_hal_synthio_synthesizer_deinit(synthio_synthesizer_obj_t *self) {
+    synthio_synth_deinit(&self->synth);
+}
+bool common_hal_synthio_synthesizer_deinited(synthio_synthesizer_obj_t *self) {
+    return synthio_synth_deinited(&self->synth);
+}
+
+uint32_t common_hal_synthio_synthesizer_get_sample_rate(synthio_synthesizer_obj_t *self) {
+    return self->synth.sample_rate;
+}
+uint8_t common_hal_synthio_synthesizer_get_bits_per_sample(synthio_synthesizer_obj_t *self) {
+    return SYNTHIO_BITS_PER_SAMPLE;
+}
+uint8_t common_hal_synthio_synthesizer_get_channel_count(synthio_synthesizer_obj_t *self) {
+    return 1;
+}
+
+void synthio_synthesizer_reset_buffer(synthio_synthesizer_obj_t *self,
+    bool single_channel_output, uint8_t channel) {
+    synthio_synth_reset_buffer(&self->synth, single_channel_output, channel);
+}
+
+audioio_get_buffer_result_t synthio_synthesizer_get_buffer(synthio_synthesizer_obj_t *self,
+    bool single_channel_output, uint8_t channel, uint8_t **buffer, uint32_t *buffer_length) {
+    self->synth.span.dur = SYNTHIO_MAX_DUR;
+    synthio_synth_synthesize(&self->synth, buffer, buffer_length, single_channel_output ? channel : 0);
+    return GET_BUFFER_MORE_DATA;
+}
+
+void synthio_synthesizer_get_buffer_structure(synthio_synthesizer_obj_t *self, bool single_channel_output,
+    bool *single_buffer, bool *samples_signed, uint32_t *max_buffer_length, uint8_t *spacing) {
+    return synthio_synth_get_buffer_structure(&self->synth, single_channel_output, single_buffer, samples_signed, max_buffer_length, spacing);
+}
+
+void common_hal_synthio_synthesizer_release_all(synthio_synthesizer_obj_t *self) {
+    synthio_span_init(&self->synth.span);
+}
+void common_hal_synthio_synthesizer_release(synthio_synthesizer_obj_t *self, mp_obj_t to_release) {
+    mp_obj_iter_buf_t iter_buf;
+    mp_obj_t iterable = mp_getiter(to_release, &iter_buf);
+    mp_obj_t item;
+    while ((item = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
+        synthio_span_change_note(&self->synth.span, mp_arg_validate_int_range(mp_obj_get_int(item), 0, 127, MP_QSTR_note), SYNTHIO_SILENCE);
+    }
+}
+
+void common_hal_synthio_synthesizer_press(synthio_synthesizer_obj_t *self, mp_obj_t to_press) {
+    mp_obj_iter_buf_t iter_buf;
+    mp_obj_t iterable = mp_getiter(to_press, &iter_buf);
+    mp_obj_t item;
+    while ((item = mp_iternext(iterable)) != MP_OBJ_STOP_ITERATION) {
+        synthio_span_change_note(&self->synth.span, SYNTHIO_SILENCE, mp_arg_validate_int_range(mp_obj_get_int(item), 0, 127, MP_QSTR_note));
+    }
+}
+
+mp_obj_t common_hal_synthio_synthesizer_get_pressed_notes(synthio_synthesizer_obj_t *self) {
+    mp_obj_tuple_t *result = MP_OBJ_TO_PTR(mp_obj_new_tuple(synthio_span_count_active_channels(&self->synth.span), NULL));
+    for (size_t i = 0, j = 0; i < CIRCUITPY_SYNTHIO_MAX_CHANNELS; i++) {
+        if (self->synth.span.note[i] != SYNTHIO_SILENCE) {
+            result->items[j++] = MP_OBJ_NEW_SMALL_INT(self->synth.span.note[i]);
+        }
+    }
+    return MP_OBJ_FROM_PTR(result);
+}
diff --git a/shared-module/synthio/Synthesizer.h b/shared-module/synthio/Synthesizer.h
new file mode 100644
index 0000000000..256b6137f2
--- /dev/null
+++ b/shared-module/synthio/Synthesizer.h
@@ -0,0 +1,53 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 Artyom Skrobov
+ * Copyright (c) 2023 Jeff Epler for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#pragma once
+
+#include "py/obj.h"
+
+#include "shared-module/synthio/__init__.h"
+
+typedef struct {
+    mp_obj_base_t base;
+    synthio_synth_t synth;
+} synthio_synthesizer_obj_t;
+
+
+// These are not available from Python because it may be called in an interrupt.
+void synthio_synthesizer_reset_buffer(synthio_synthesizer_obj_t *self,
+    bool single_channel_output,
+    uint8_t channel);
+
+audioio_get_buffer_result_t synthio_synthesizer_get_buffer(synthio_synthesizer_obj_t *self,
+    bool single_channel_output,
+    uint8_t channel,
+    uint8_t **buffer,
+    uint32_t *buffer_length); // length in bytes
+
+void synthio_synthesizer_get_buffer_structure(synthio_synthesizer_obj_t *self, bool single_channel_output,
+    bool *single_buffer, bool *samples_signed,
+    uint32_t *max_buffer_length, uint8_t *spacing);
diff --git a/shared-module/synthio/__init__.c b/shared-module/synthio/__init__.c
index e69de29bb2..7ac8e47746 100644
--- a/shared-module/synthio/__init__.c
+++ b/shared-module/synthio/__init__.c
@@ -0,0 +1,169 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 Artyom Skrobov
+ * Copyright (c) 2023 Jeff Epler for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "shared-module/synthio/__init__.h"
+#include "py/runtime.h"
+
+STATIC const int16_t square_wave[] = {-32768, 32767};
+
+STATIC const uint16_t notes[] = {8372, 8870, 9397, 9956, 10548, 11175, 11840,
+                                 12544, 13290, 14080, 14917, 15804}; // 9th octave
+
+int synthio_span_count_active_channels(synthio_midi_span_t *span) {
+    int result = 0;
+    for (int i = 0; i < CIRCUITPY_SYNTHIO_MAX_CHANNELS; i++) {
+        if (span->note[i] != SYNTHIO_SILENCE) {
+            result += 1;
+        }
+    }
+    return result;
+}
+
+
+void synthio_synth_synthesize(synthio_synth_t *synth, uint8_t **bufptr, uint32_t *buffer_length, uint8_t channel) {
+
+    if (channel == synth->other_channel) {
+        *buffer_length = synth->last_buffer_length;
+        *bufptr = (uint8_t *)(synth->buffers[synth->other_buffer_index] + channel);
+        return;
+    }
+
+    synth->buffer_index = !synth->buffer_index;
+    synth->other_channel = 1 - channel;
+    synth->other_buffer_index = synth->buffer_index;
+    int16_t *out_buffer = (int16_t *)(void *)synth->buffers[synth->buffer_index];
+
+    uint16_t dur = MIN(SYNTHIO_MAX_DUR, synth->span.dur);
+    synth->span.dur -= dur;
+    memset(out_buffer, 0, synth->buffer_length);
+
+    int32_t sample_rate = synth->sample_rate;
+    int active_channels = synthio_span_count_active_channels(&synth->span);
+    const int16_t *waveform = synth->waveform;
+    uint32_t waveform_length = synth->waveform_length;
+    if (active_channels) {
+        int16_t loudness = 0x3fff / (1 + active_channels);
+        for (int chan = 0; chan < CIRCUITPY_SYNTHIO_MAX_CHANNELS; chan++) {
+            if (synth->span.note[chan] == SYNTHIO_SILENCE) {
+                synth->accum[chan] = 0;
+                continue;
+            }
+            uint8_t octave = synth->span.note[chan] / 12;
+            uint16_t base_freq = notes[synth->span.note[chan] % 12];
+            uint32_t accum = synth->accum[chan];
+#define SHIFT (16)
+            // rate = base_freq * waveform_length
+            // den = sample_rate * 2 ^ (10 - octave)
+            // den = sample_rate * 2 ^ 10 / 2^octave
+            // dds_rate = 2^SHIFT * rate / den
+            // dds_rate = 2^(SHIFT-10+octave) * base_freq * waveform_length / sample_rate
+            uint32_t dds_rate = (sample_rate / 2 + ((uint64_t)(base_freq * waveform_length) << (SHIFT - 10 + octave))) / sample_rate;
+
+            for (uint16_t i = 0; i < dur; i++) {
+                accum += dds_rate;
+                if (accum > waveform_length << SHIFT) {
+                    accum -= waveform_length << SHIFT;
+                }
+                int16_t idx = accum >> SHIFT;
+                out_buffer[i] += (waveform[idx] * loudness) / 65536;
+            }
+            synth->accum[chan] = accum;
+        }
+    }
+
+    *buffer_length = synth->last_buffer_length = dur * SYNTHIO_BYTES_PER_SAMPLE;
+    *bufptr = (uint8_t *)out_buffer;
+}
+
+void synthio_synth_reset_buffer(synthio_synth_t *synth, bool single_channel_output, uint8_t channel) {
+    if (single_channel_output && channel == 1) {
+        return;
+    }
+    synth->other_channel = -1;
+}
+
+bool synthio_synth_deinited(synthio_synth_t *synth) {
+    return synth->buffers[0] == NULL;
+}
+
+void synthio_synth_deinit(synthio_synth_t *synth) {
+    m_del(uint8_t, synth->buffers[0], synth->buffer_length);
+    m_del(uint8_t, synth->buffers[1], synth->buffer_length);
+    synth->buffers[0] = NULL;
+    synth->buffers[1] = NULL;
+}
+
+void synthio_synth_init(synthio_synth_t *synth, uint16_t max_dur) {
+    synth->buffer_length = MIN(SYNTHIO_MAX_DUR, max_dur) * SYNTHIO_BYTES_PER_SAMPLE;
+    synth->buffers[0] = m_malloc(synth->buffer_length, false);
+    synth->buffers[1] = m_malloc(synth->buffer_length, false);
+    synth->other_channel = -1;
+}
+
+void synthio_synth_get_buffer_structure(synthio_synth_t *synth, bool single_channel_output,
+    bool *single_buffer, bool *samples_signed, uint32_t *max_buffer_length, uint8_t *spacing) {
+    *single_buffer = false;
+    *samples_signed = true;
+    *max_buffer_length = synth->buffer_length;
+    *spacing = 1;
+}
+
+void synthio_synth_parse_waveform(mp_buffer_info_t *bufinfo_waveform, mp_obj_t waveform_obj) {
+    *bufinfo_waveform = ((mp_buffer_info_t) { .buf = (void *)square_wave, .len = 4 });
+
+    if (waveform_obj != mp_const_none) {
+        mp_get_buffer_raise(waveform_obj, bufinfo_waveform, MP_BUFFER_READ);
+        if (bufinfo_waveform->typecode != 'h') {
+            mp_raise_ValueError_varg(translate("%q must be array of type 'h'"), MP_QSTR_waveform);
+        }
+    }
+    mp_arg_validate_length_range(bufinfo_waveform->len / 2, 2, 1024, MP_QSTR_waveform);
+}
+
+void synthio_span_init(synthio_midi_span_t *span) {
+    span->dur = 0;
+    for (size_t i = 0; i < CIRCUITPY_SYNTHIO_MAX_CHANNELS; i++) { span->note[i] = SYNTHIO_SILENCE;
+    }
+}
+
+STATIC int find_channel_with_note(const synthio_midi_span_t *span, uint8_t note) {
+    for (int i = 0; i < CIRCUITPY_SYNTHIO_MAX_CHANNELS; i++) {
+        if (span->note[i] == note) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+bool synthio_span_change_note(synthio_midi_span_t *span, uint8_t old_note, uint8_t new_note) {
+    int channel = find_channel_with_note(span, old_note);
+    if (channel != -1) {
+        span->note[channel] = new_note;
+        return true;
+    }
+    return false;
+}
diff --git a/shared-module/synthio/__init__.h b/shared-module/synthio/__init__.h
index d9d98a5341..e14e5ead10 100644
--- a/shared-module/synthio/__init__.h
+++ b/shared-module/synthio/__init__.h
@@ -24,9 +24,41 @@
  * THE SOFTWARE.
  */
 
-#ifndef MICROPY_INCLUDED_SHARED_MODULE_SYNTHIO__INIT__H
-#define MICROPY_INCLUDED_SHARED_MODULE_SYNTHIO__INIT__H
+#pragma once
+
+#define SYNTHIO_BITS_PER_SAMPLE (16)
+#define SYNTHIO_BYTES_PER_SAMPLE (SYNTHIO_BITS_PER_SAMPLE / 8)
+#define SYNTHIO_MAX_DUR (256)
+#define SYNTHIO_SILENCE (0x80)
 
 #include "shared-module/audiocore/__init__.h"
 
-#endif  // MICROPY_INCLUDED_SHARED_MODULE_SYNTHIO__INIT__H
+typedef struct {
+    uint16_t dur;
+    uint8_t note[CIRCUITPY_SYNTHIO_MAX_CHANNELS];
+} synthio_midi_span_t;
+
+typedef struct {
+    uint32_t sample_rate;
+    int16_t *buffers[2];
+    const int16_t *waveform;
+    uint16_t buffer_length;
+    uint16_t last_buffer_length;
+    uint8_t other_channel, buffer_index, other_buffer_index;
+    uint16_t waveform_length;
+    synthio_midi_span_t span;
+    uint32_t accum[CIRCUITPY_SYNTHIO_MAX_CHANNELS];
+} synthio_synth_t;
+
+void synthio_span_init(synthio_midi_span_t *span);
+void synthio_synth_synthesize(synthio_synth_t *synth, uint8_t **buffer, uint32_t *buffer_length, uint8_t channel);
+void synthio_synth_deinit(synthio_synth_t *synth);
+bool synthio_synth_deinited(synthio_synth_t *synth);
+void synthio_synth_init(synthio_synth_t *synth, uint16_t max_dur);
+void synthio_synth_get_buffer_structure(synthio_synth_t *synth, bool single_channel_output,
+    bool *single_buffer, bool *samples_signed, uint32_t *max_buffer_length, uint8_t *spacing);
+void synthio_synth_reset_buffer(synthio_synth_t *synth, bool single_channel_output, uint8_t channel);
+void synthio_synth_parse_waveform(mp_buffer_info_t *bufinfo_waveform, mp_obj_t waveform_obj);
+
+bool synthio_span_change_note(synthio_midi_span_t *span, uint8_t old_note, uint8_t new_note);
+int synthio_span_count_active_channels(synthio_midi_span_t *span);
diff --git a/tests/circuitpython/miditrack.py b/tests/circuitpython/miditrack.py
new file mode 100644
index 0000000000..53a8ca631d
--- /dev/null
+++ b/tests/circuitpython/miditrack.py
@@ -0,0 +1,20 @@
+import array
+
+try:
+    from synthio import MidiTrack
+    from audiocore import get_buffer, get_structure
+except ImportError:
+    print("SKIP")
+    raise SystemExit
+
+SCORE = b"\0\x90@\0\x20\x90b\0\x20\x80@\0\0\x80\b\0"
+
+with MidiTrack(SCORE, sample_rate=8000, tempo=640) as m:
+    print(get_structure(m))
+    print(get_buffer(m))
+
+with MidiTrack(
+    SCORE, sample_rate=8000, tempo=640, waveform=array.array("h", [0, 32767, 0, -32768])
+) as m:
+    print(get_structure(m))
+    print(get_buffer(m))
diff --git a/tests/circuitpython/miditrack.py.exp b/tests/circuitpython/miditrack.py.exp
new file mode 100644
index 0000000000..be5eef1d0b
--- /dev/null
+++ b/tests/circuitpython/miditrack.py.exp
@@ -0,0 +1,4 @@
+(0, 1, 512, 1)
+(1, b'\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\xff\x0f\xff\x0f')
+(0, 1, 512, 1)
+(1, b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x01\xf0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\xff\x0f\x00\x00\x00\x00')
diff --git a/tests/circuitpython/synthesizer.py b/tests/circuitpython/synthesizer.py
new file mode 100644
index 0000000000..bdb273f861
--- /dev/null
+++ b/tests/circuitpython/synthesizer.py
@@ -0,0 +1,24 @@
+import struct
+import synthio
+import audiocore
+
+
+def dump_samples():
+    print(struct.unpack("12h", audiocore.get_buffer(s)[1][:24]))
+
+
+s = synthio.Synthesizer(sample_rate=8000)
+print(s.pressed)
+dump_samples()
+
+s.press((80,))
+print(s.pressed)
+dump_samples()
+
+s.press((91,))
+print(s.pressed)
+dump_samples()
+
+s.release_then_press((80,))
+print(s.pressed)
+dump_samples()
diff --git a/tests/circuitpython/synthesizer.py.exp b/tests/circuitpython/synthesizer.py.exp
new file mode 100644
index 0000000000..4296662d60
--- /dev/null
+++ b/tests/circuitpython/synthesizer.py.exp
@@ -0,0 +1,8 @@
+()
+(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
+(80,)
+(-4095, -4095, -4095, -4095, 4095, 4095, 4095, 4095, 4095, -4095, -4095, -4095)
+(80, 91)
+(0, 0, 5460, 5460, 0, -5460, -5460, 0, 5460, 5460, 0, 0)
+(91,)
+(-4095, 4095, 4095, 4095, -4095, -4095, 4095, 4095, 4095, -4095, -4095, 4095)
diff --git a/tests/unix/extra_coverage.py.exp b/tests/unix/extra_coverage.py.exp
index 8014dd3010..c750ca0e95 100644
--- a/tests/unix/extra_coverage.py.exp
+++ b/tests/unix/extra_coverage.py.exp
@@ -30,20 +30,21 @@ ame__
 mport 
 
 builtins        micropython     _asyncio        _thread
-_uasyncio       aesio           array           binascii
-bitmaptools     btree           cexample        cmath
-collections     cppexample      displayio       errno
-ffi             framebuf        gc              hashlib
-json            math            qrio            rainbowio
-re              struct          sys             termios
-traceback       ubinascii       uctypes         uerrno
-uheapq          uio             ujson           ulab
-ulab.numpy      ulab.numpy.fft  ulab.numpy.linalg
-ulab.scipy      ulab.scipy.linalg
-ulab.scipy.optimize             ulab.scipy.signal
-ulab.scipy.special              ulab.utils      uos
-urandom         ure             uselect         utime
-utimeq          uzlib           zlib
+_uasyncio       aesio           array           audiocore
+audiomixer      binascii        bitmaptools     btree
+cexample        cmath           collections     cppexample
+displayio       errno           ffi             framebuf
+gc              hashlib         json            math
+qrio            rainbowio       re              struct
+synthio         sys             termios         traceback
+ubinascii       uctypes         uerrno          uheapq
+uio             ujson           ulab            ulab.numpy
+ulab.numpy.fft  ulab.numpy.linalg               ulab.scipy
+ulab.scipy.linalg               ulab.scipy.optimize
+ulab.scipy.signal               ulab.scipy.special
+ulab.utils      uos             urandom         ure
+uselect         utime           utimeq          uzlib
+zlib
 ime
 
 utime           utimeq