Demonstrate cool new CircuitPython synthio.Synthesizer as wavetable MIDI synth, using new synthio.Envelope feature

midi_env_synthio_synth.py

#
# midi_env_synthio_synth.py -- Demonstrate new synthio.Synthesizer as wavetable MIDI synth
# using new synthio.Envelope feature in https://github.com/adafruit/circuitpython/pull/7862
#
# 30 Apr 2023 - @todbot / Tod Kurt
#
# Hooked up to generic I2S DAC
# - MIDI key velocity controls attack & release times
# - MIDI modwheel (CC1) controls wave mix between saw and a granular AKWF wave
#

import time
import board, analogio
import audiobusio, audiomixer
import synthio
import ulab.numpy as np
import usb_midi
import adafruit_midi
from adafruit_midi.note_on import NoteOn
from adafruit_midi.note_off import NoteOff
from adafruit_midi.control_change import ControlChange
import neopixel

SAMPLE_RATE = 28000  # clicks @ 36kHz & 48kHz on rp2040
SAMPLE_SIZE = 200
VOLUME = 12000

# qtpy rp2040 SPI pins
lck_pin, bck_pin, dat_pin  = board.MISO, board.MOSI, board.SCK

# synth engine setup

waveform = np.zeros(SAMPLE_SIZE, dtype=np.int16)  # intially all zeros (silence)

# "amp_env" will be replaced on every key press (and key release?)
amp_env = synthio.Envelope(attack_time=0.1, decay_time = 0.05, release_time=0.2,
                           attack_level=1, sustain_level=0.8)
synth = synthio.Synthesizer(sample_rate=SAMPLE_RATE, waveform=waveform, envelope=amp_env)

audio = audiobusio.I2SOut(bit_clock=bck_pin, word_select=lck_pin, data=dat_pin)
mixer = audiomixer.Mixer(voice_count=1, sample_rate=SAMPLE_RATE, channel_count=1,
                         bits_per_sample=16, samples_signed=True, buffer_size=2048 )
audio.play(mixer)
mixer.voice[0].play(synth)

midi = adafruit_midi.MIDI(midi_in=usb_midi.ports[0], in_channel=0 )

led = neopixel.NeoPixel(board.NEOPIXEL, 1, brightness=0.2)

# waveforms setup
wave_saw = np.linspace(VOLUME, -VOLUME, num=SAMPLE_SIZE, dtype=np.int16)
# akwf_0018_08 I think
wave_weird1 = np.array((198,2776,5441,8031,10454,12653,14609,16333,17824,19130,20260,21227,22043,22721,23269,23699,24019,24243,24385,24461,18630,-26956,-28048,-29175,-30249,-31227,-32073,-32631,-32359,-31817,-30941,-29663,-27900,-25596,-22591,-18834,-14291,-9016,-3212,2794,8624,13943,18544,22353,25408,27780,29553,30855,31751,32315,32611,32687,32593,32351,31983,31491,30871,30097,28895,-28240,-30489,-31343,-31975,-32431,-32697,-32767,-32615,-32217,-31525,-30489,-29035,-27090,-24519,-21237,-17178,-12339,-6829,-902,5081,10748,15805,20102,23615,26396,28510,30109,31245,31995,31955,31437,30729,29887,28943,27908,26784,25560,24077,22781,-22207,-22735,-22709,-22471,-22065,-21497,-20773,-19896,-18872,-17698,-16361,-14857,-13141,-11206,-9054,-6717,-4259,-1796,522,2548,4167,5339,6079,6445,6503,6319,5949,5449,4847,4183,3480,2756,2028,1304,590,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-478,-1168,-1882,-2596,-3336,-4074,-4795,-5487,-6119,-6669,-7095,-7357,-7399,-7157,-6559,-5543,-4076,-2132,), dtype=np.int16)
wave_weird1 = wave_weird1 * 0.5 # lower volume a bit

# map s range a1-a2 to b1-b2
def map_range(s, a1, a2, b1, b2):  return  b1 + ((s - a1) * (b2 - b1) / (a2 - a1))

# mix between values a and b, works with numpy arrays too, t ranges 0-1
def lerp(a, b, t):  return (1-t)*a + t*b

waveform[:] = wave_saw
wave_mix = 0
last_debug_time = time.monotonic()

print("midi_env_synthio_synth")

while True:
    # handle midi
    msg = midi.receive()
    if isinstance(msg, NoteOn) and msg.velocity != 0:
        print("noteOn: ", msg.note, "vel=", msg.velocity)
        led.fill(0xff00ff)
        # can't do this:
        # amp_env.attack_time = map_range( msg.velocity, 1,127, 3, 0.1)
        # instead, replace entire synthio.amp_env
        # NOTE: this means new notes overwrite envelope of held notes
        attack_time = map_range( msg.velocity, 1,127, 3, 0.05)
        release_time = map_range( msg.velocity, 1,127, 3, 0.1)
        amp_env = synthio.Envelope(attack_time = attack_time,
                                   decay_time = amp_env.decay_time,
                                   release_time = release_time,
                                   attack_level = amp_env.attack_level,
                                   sustain_level = amp_env.sustain_level)
        synth.envelope = amp_env
        synth.press( (msg.note,) )
    elif isinstance(msg,NoteOff) or isinstance(msg,NoteOn) and msg.velocity==0:
        print("noteOff:", msg.note, "vel=", msg.velocity)
        led.fill(0x00000)
        # what about changing release_time based on noteoff velocity?
        # yes that's possible, but some keyboards (like Arturia Keystep),
        # send fixed noteoff velocity, so we fake it by using noteon velocity
        # release_time = map_range( msg.velocity, 1,127, 3, 0.2)
        # amp_env = synthio.Envelope(attack_time=amp_env.attack_time,
        #                            decay_time=amp_env.decay_time,
        #                            release_time=release_time,
        #                            attack_level=amp_env.attac`k_level,
        #                            sustain_level=amp_env.sustain_level)
        # synth.envelope = amp_env
        synth.release( (msg.note,) )
    elif isinstance(msg,ControlChange):
        print("controlChange", msg.control, "=", msg.value)
        if msg.control == 1: # mod wheel
            wave_mix = msg.value / 127

    waveform[:] = lerp( wave_saw, wave_weird1, wave_mix )

    # debug info
    if time.monotonic() - last_debug_time > 0.5:
        last_debug_time = time.monotonic()
        print("wave_mix: %.2f" % wave_mix)

Here's a little demo of the above program, using a QTPY RP2040 and PCM5102 cheapie I2S DAC.

synthio_envelopetest2.mp4