The underlying routine can return numbers for higher and lower
octaves. Other bits of the code might have frequency limitations
but that doesn't mean we shouldn't let someone get a ~4Hz "note"
by sending in (-12), because that's actually totally plausible as
an LFO frequency.
Semi-incompatible name change: The method `release_then_press`
is now `change`. For now a compatibility alias is supported.
Everywhere a `NoteSequence` was accepted, a single note is now accepted.
So for instance, `synth.press(30)` can be written instead of requiring
``synth.press((30,))`. The same goes for `change.retrigger`, which
will accept a single LFO or a sequence.
When there's no sustain, the release step needs to be calculated from
the attack level, not the sustain level. Otherwise, contrary to intent,
this leads to the actual release taking a loooonnngg time.
A note can be placed in the center (panning=0) or moved to just the left
(panning=1) or right (panning=-1) channels. Fractional panning values
place it partially in both channels.
Now the vibrato 'units' are 1.0 = one octave, 1/12 = one semitone,
1/1200 = one cent. Before, the units were somewhat arbitrary and were not
perceptually "symmetrical" around the base frequency.
For vibrato_depth = 1/12 and base frequency of 440,
before: pitch from 403.33 to 476.67Hz, not corresponding to any notes
after: pitch from 415.30 to 466.16Hz, corresponding to G# and A#
this has the side effect of making some notes more accurate, the new
frequency= value in the test is closer to the true midi frequency of
830.609...Hz.
and re-vamp overall envelope calculation again.
Now, if you set a low overall attack level like 0.2 this avoids the
"diminishing volume" effect when many notes sound at once. You need
simply choose a maximum attack level that is appropriate for the max
number of voices that will actually be played.
This class allows much more expressive sound synthesis:
* tremolo & vibrato
* arbitrary frequency
* different evelope & waveform per note
* all properties dynamically settable from Python code
