Let's get to some real-world examples! These are adapted from Tod Kurt's excellent CircuitPython Synthio Tricks page.
# SPDX-FileCopyrightText: 2023 John Park and @todbot / Tod Kurt
#
# SPDX-License-Identifier: MIT
import time
import board
import digitalio
import synthio
# for PWM audio with an RC filter
# import audiopwmio
# audio = audiopwmio.PWMAudioOut(board.GP10)
# for I2S audio with external I2S DAC board
import audiobusio
# I2S on Audio BFF or Amp BFF on QT Py:
# audio = audiobusio.I2SOut(bit_clock=board.A3, word_select=board.A2, data=board.A1)
# I2S audio on PropMaker Feather RP2040
power = digitalio.DigitalInOut(board.EXTERNAL_POWER)
power.switch_to_output(value=True)
audio = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DATA)
synth = synthio.Synthesizer(sample_rate=44100)
audio.play(synth)
while True:
synth.press(65) # midi note 65 = F4
time.sleep(0.5)
synth.release(65) # release the note we pressed
time.sleep(2)
# SPDX-FileCopyrightText: 2023 John Park and @todbot / Tod Kurt
#
# SPDX-License-Identifier: MIT
import time
import board
import digitalio
import synthio
# for PWM audio with an RC filter
# import audiopwmio
# audio = audiopwmio.PWMAudioOut(board.GP10)
# for I2S audio with external I2S DAC board
import audiobusio
# I2S on Audio BFF or Amp BFF on QT Py:
# audio = audiobusio.I2SOut(bit_clock=board.A3, word_select=board.A2, data=board.A1)
# I2S audio on PropMaker Feather RP2040
power = digitalio.DigitalInOut(board.EXTERNAL_POWER)
power.switch_to_output(value=True)
audio = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DATA)
synth = synthio.Synthesizer(sample_rate=44100)
audio.play(synth)
while True:
synth.press((65, 69, 72)) # midi note 65 = F4
time.sleep(1)
synth.release((65, 69, 72)) # release the note we pressed
time.sleep(2)
# SPDX-FileCopyrightText: 2023 John Park and @todbot / Tod Kurt
#
# SPDX-License-Identifier: MIT
import time
import board
import digitalio
import audiomixer
import synthio
# for PWM audio with an RC filter
# import audiopwmio
# audio = audiopwmio.PWMAudioOut(board.GP10)
# for I2S audio with external I2S DAC board
import audiobusio
# I2S on Audio BFF or Amp BFF on QT Py:
# audio = audiobusio.I2SOut(bit_clock=board.A3, word_select=board.A2, data=board.A1)
# I2S audio on PropMaker Feather RP2040
power = digitalio.DigitalInOut(board.EXTERNAL_POWER)
power.switch_to_output(value=True)
audio = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DATA)
mixer = audiomixer.Mixer(channel_count=1, sample_rate=22050, buffer_size=2048)
synth = synthio.Synthesizer(channel_count=1, sample_rate=22050)
audio.play(mixer)
mixer.voice[0].play(synth)
mixer.voice[0].level = 0.4
while True:
synth.press((65, 69, 72)) # midi note 65 = F4
time.sleep(0.5)
synth.release((65, 69, 72)) # release the note we pressed
time.sleep(0.5)
mixer.voice[0].level = (mixer.voice[0].level - 0.1) % 0.4 # reduce volume each pass
# SPDX-FileCopyrightText: 2023 John Park and @todbot / Tod Kurt
#
# SPDX-License-Identifier: MIT
import time
import board
import digitalio
import audiomixer
import synthio
# for PWM audio with an RC filter
#import audiopwmio
#audio = audiopwmio.PWMAudioOut(board.GP10)
# for I2S audio with external I2S DAC board
import audiobusio
# I2S on Audio BFF or Amp BFF on QT Py:
# audio = audiobusio.I2SOut(bit_clock=board.A3, word_select=board.A2, data=board.A1)
# I2S audio on PropMaker Feather RP2040
power = digitalio.DigitalInOut(board.EXTERNAL_POWER)
power.switch_to_output(value=True)
audio = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DATA)
mixer = audiomixer.Mixer(channel_count=1, sample_rate=22050, buffer_size=2048)
amp_env_slow = synthio.Envelope(
attack_time=0.2,
sustain_level=1.0,
release_time=0.8
)
amp_env_fast = synthio.Envelope(
attack_time=0.1,
sustain_level=0.5,
release_time=0.2
)
synth = synthio.Synthesizer(channel_count=1, sample_rate=22050, envelope=amp_env_slow)
audio.play(mixer)
mixer.voice[0].play(synth)
mixer.voice[0].level = 0.2
while True:
synth.envelope = amp_env_slow
synth.press(46)
time.sleep(1.25)
synth.release(46)
time.sleep(1.25)
synth.envelope = amp_env_fast
synth.press(51)
time.sleep(1.25)
synth.release(51)
time.sleep(1.25)
# SPDX-FileCopyrightText: 2023 John Park and @todbot / Tod Kurt
#
# SPDX-License-Identifier: MIT
import time
import board
import digitalio
import audiomixer
import synthio
# for PWM audio with an RC filter
# import audiopwmio
# audio = audiopwmio.PWMAudioOut(board.GP10)
# for I2S audio with external I2S DAC board
import audiobusio
# I2S on Audio BFF or Amp BFF on QT Py:
# audio = audiobusio.I2SOut(bit_clock=board.A3, word_select=board.A2, data=board.A1)
# I2S audio on PropMaker Feather RP2040
power = digitalio.DigitalInOut(board.EXTERNAL_POWER)
power.switch_to_output(value=True)
audio = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DATA)
mixer = audiomixer.Mixer(channel_count=1, sample_rate=22050, buffer_size=2048)
amp_env_slow = synthio.Envelope(
attack_time=0.2,
sustain_level=1.0,
release_time=0.8
)
synth = synthio.Synthesizer(channel_count=1, sample_rate=22050, envelope=amp_env_slow)
# set up filters
frequency = 2000
resonance = 1.5
lpf = synth.low_pass_filter(frequency, resonance)
hpf = synth.high_pass_filter(frequency, resonance)
bpf = synth.band_pass_filter(frequency, resonance)
note1 = synthio.Note(frequency=330, filter=None)
audio.play(mixer)
mixer.voice[0].play(synth)
mixer.voice[0].level = 0.2
while True:
# no filter
note1.filter = None
synth.press(note1)
time.sleep(1.25)
synth.release(note1)
time.sleep(1.25)
# lpf
note1.filter = lpf
synth.press(note1)
time.sleep(1.25)
synth.release(note1)
time.sleep(1.25)
# hpf
note1.filter = hpf
synth.press(note1)
time.sleep(1.25)
synth.release(note1)
time.sleep(1.25)
# bpf
note1.filter = bpf
synth.press(note1)
time.sleep(1.25)
synth.release(note1)
time.sleep(1.25)
# SPDX-FileCopyrightText: 2023 John Park and @todbot / Tod Kurt
#
# SPDX-License-Identifier: MIT
import board
import digitalio
import audiomixer
import synthio
import usb_midi
import adafruit_midi
from adafruit_midi.note_on import NoteOn
from adafruit_midi.note_off import NoteOff
# note for ESP32-S2 boards, due to not enough available endpoints,
# to enable USB MIDI, create a "boot.py" with following in it, then power cycle board:
# import usb_hid
# import usb_midi
# usb_hid.disable()
# usb_midi.enable()
# print("enabled USB MIDI, disabled USB HID")
# for PWM audio with an RC filter
# import audiopwmio
# audio = audiopwmio.PWMAudioOut(board.GP10)
# for I2S audio with external I2S DAC board
import audiobusio
# I2S on Audio BFF or Amp BFF on QT Py:
# audio = audiobusio.I2SOut(bit_clock=board.A3, word_select=board.A2, data=board.A1)
# I2S audio on PropMaker Feather RP2040
power = digitalio.DigitalInOut(board.EXTERNAL_POWER)
power.switch_to_output(value=True)
audio = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DATA)
mixer = audiomixer.Mixer(channel_count=1, sample_rate=22050, buffer_size=2048)
midi = adafruit_midi.MIDI(midi_in=usb_midi.ports[0], in_channel=0)
amp_env_med = synthio.Envelope(
attack_time=0.05,
sustain_level=0.8,
release_time=0.2
)
synth = synthio.Synthesizer(channel_count=1, sample_rate=22050, envelope=amp_env_med)
note1 = synthio.Note(frequency=330, filter=None)
audio.play(mixer)
mixer.voice[0].play(synth)
mixer.voice[0].level = 0.2
while True:
msg = midi.receive()
if isinstance(msg, NoteOn) and msg.velocity != 0:
print("noteOn: ", msg.note, "vel:", msg.velocity)
note1.frequency = synthio.midi_to_hz(msg.note)
synth.press(note1)
elif isinstance(msg, NoteOff) or isinstance(msg, NoteOn) and msg.velocity == 0:
print("noteOff:", msg.note, "vel:", msg.velocity)
note1.frequency = synthio.midi_to_hz(msg.note)
synth.release(note1)
# SPDX-FileCopyrightText: 2023 John Park and @todbot / Tod Kurt
#
# SPDX-License-Identifier: MIT
import board
import busio
import digitalio
import audiomixer
import synthio
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
# note for ESP32-S2 boards, due to not enough available endpoints,
# to enable USB MIDI, create a "boot.py" with following in it, then power cycle board:
# import usb_hid
# import usb_midi
# usb_hid.disable()
# usb_midi.enable()
# print("enabled USB MIDI, disabled USB HID")
# for PWM audio with an RC filter
# import audiopwmio
# audio = audiopwmio.PWMAudioOut(board.GP10)
# for I2S audio with external I2S DAC board
import audiobusio
# I2S on Audio BFF or Amp BFF on QT Py:
# audio = audiobusio.I2SOut(bit_clock=board.A3, word_select=board.A2, data=board.A1)
# I2S audio on PropMaker Feather RP2040
power = digitalio.DigitalInOut(board.EXTERNAL_POWER)
power.switch_to_output(value=True)
audio = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DATA)
mixer = audiomixer.Mixer(channel_count=1, sample_rate=22050, buffer_size=2048)
midi_channel = 1
uart = busio.UART(tx=board.TX, rx=board.RX, baudrate=31250, timeout=0.001)
midi_usb = adafruit_midi.MIDI(midi_in=usb_midi.ports[0], in_channel=0)
midi_uart = adafruit_midi.MIDI(midi_in=uart, in_channel=midi_channel-1)
amp_env_med = synthio.Envelope(
attack_time=0.05,
sustain_level=0.8,
release_time=0.2
)
synth = synthio.Synthesizer(channel_count=1, sample_rate=22050, envelope=amp_env_med)
# set up filters
filter_freq = 4000
filter_res = 0.5
filter_freq_lo = 100 # filter lowest freq
filter_freq_hi = 4500 # filter highest freq
filter_res_lo = 0.5 # filter q lowest value
filter_res_hi = 2.0 # filter q highest value
lpf = synth.low_pass_filter(filter_freq, filter_res)
note1 = synthio.Note(frequency=330, filter=lpf)
audio.play(mixer)
mixer.voice[0].play(synth)
mixer.voice[0].level = 0.2
def map_range(s, a1, a2, b1, b2):
return b1 + ((s - a1) * (b2 - b1) / (a2 - a1))
while True:
note1.filter = synth.low_pass_filter(filter_freq, filter_res)
msg = midi_uart.receive() or midi_usb.receive()
if isinstance(msg, NoteOn) and msg.velocity != 0:
print("noteOn: ", msg.note, "vel:", msg.velocity)
note1.frequency = synthio.midi_to_hz(msg.note)
synth.press(note1)
elif isinstance(msg, NoteOff) or isinstance(msg, NoteOn) and msg.velocity == 0:
print("noteOff:", msg.note, "vel:", msg.velocity)
note1.frequency = synthio.midi_to_hz(msg.note)
synth.release(note1)
elif isinstance(msg, ControlChange):
print("CC", msg.control, "=", msg.value)
if msg.control == 21: # filter cutoff
filter_freq = map_range(msg.value, 0, 127, filter_freq_lo, filter_freq_hi)
elif msg.control == 22: # filter Q
filter_res = map_range(msg.value, 0, 127, filter_res_lo, filter_res_hi)
elif msg.control == 7: # volume
mixer.voice[0].level = map_range(msg.value, 0, 127, 0.0, 1.0)
# SPDX-FileCopyrightText: 2023 John Park and @todbot / Tod Kurt
#
# SPDX-License-Identifier: MIT
import board
import digitalio
import audiomixer
import synthio
# for PWM audio with an RC filter
# import audiopwmio
# audio = audiopwmio.PWMAudioOut(board.GP10)
# for I2S audio with external I2S DAC board
import audiobusio
# I2S on Audio BFF or Amp BFF on QT Py:
# audio = audiobusio.I2SOut(bit_clock=board.A3, word_select=board.A2, data=board.A1)
# I2S audio on PropMaker Feather RP2040
power = digitalio.DigitalInOut(board.EXTERNAL_POWER)
power.switch_to_output(value=True)
audio = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DATA)
mixer = audiomixer.Mixer(channel_count=1, sample_rate=44100, buffer_size=4096)
synth = synthio.Synthesizer(channel_count=1, sample_rate=44100)
audio.play(mixer)
mixer.voice[0].play(synth)
mixer.voice[0].level = 0.1
lfo = synthio.LFO(rate=0.6, scale=0.05) # 1 Hz lfo at 0.25%
midi_note = 52
note = synthio.Note(synthio.midi_to_hz(midi_note), bend=lfo)
synth.press(note)
while True:
pass
# SPDX-FileCopyrightText: 2023 John Park and @todbot / Tod Kurt
#
# SPDX-License-Identifier: MIT
import time
import board
import digitalio
import audiomixer
import synthio
# for PWM audio with an RC filter
# import audiopwmio
# audio = audiopwmio.PWMAudioOut(board.GP10)
# for I2S audio with external I2S DAC board
import audiobusio
# I2S on Audio BFF or Amp BFF on QT Py:
# audio = audiobusio.I2SOut(bit_clock=board.A3, word_select=board.A2, data=board.A1)
# I2S audio on PropMaker Feather RP2040
power = digitalio.DigitalInOut(board.EXTERNAL_POWER)
power.switch_to_output(value=True)
audio = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DATA)
mixer = audiomixer.Mixer(channel_count=1, sample_rate=44100, buffer_size=4096)
synth = synthio.Synthesizer(channel_count=1, sample_rate=44100)
audio.play(mixer)
mixer.voice[0].play(synth)
mixer.voice[0].level = 0.2
lfo_tremolo = synthio.LFO(rate=0.8, scale=0.3, offset=0.7)
midi_note = 50
note1 = synthio.Note(synthio.midi_to_hz(midi_note), amplitude=lfo_tremolo)
synth.press(note1)
while True:
print(lfo_tremolo.value)
time.sleep(0.05)
Page last edited January 22, 2025
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