A CircuitPython class for generating wind chime and bell sounds using synthio.

The CedarGrove CircuitPython Chime class provides synthio note overtones and envelopes developed from a combination of tubular chime algorithms and empirical (practical) models. Three chime voices are included in the class (Voice.Tubular, Voice.Bell, and Voice.Perfect) as well as selectable chime and striker materials. The Scales class contains a library of common wind chime and bell scales in a collection of Scientific Pitch Notation (SPN) lists.

The Chime class is instantiated after an MCU board-specific audio output object is defined. The audio output object can be an Analog DAC or PWM GPIO pin as well as an I2S DAC output (as in the simpletest example). Chime notes are then played by the Chime.strike(root_note, amplitude) function.

This class depends on:

• Adafruit CircuitPython
• CedarGrove CircuitPython_MIDI_Tools

Please ensure all dependencies are available on the CircuitPython filesystem. This is easily achieved by downloading the Adafruit library and driver bundle or individual libraries can be installed using circup.

import time
import board
import random
import audiobusio
import audiomixer
from cedargrove_chime import Chime, Scale, Voice, Material, Striker

# Instantiate I2S output and mixer buffer for synthesizer
audio_output = audiobusio.I2SOut(
    bit_clock=board.D12, word_select=board.D9, data=board.D6
)
mixer = audiomixer.Mixer(
    sample_rate=11020, buffer_size=4096, voice_count=1, channel_count=1
)
audio_output.play(mixer)
mixer.voice[0].level = 1.0

# Instantiate the chime synth with mostly default parameters
chime = Chime(mixer.voice[0], scale=Scale.HarryDavidPear)

# Play scale notes sequentially
for index, note in enumerate(chime.scale):
    chime.strike(note, 1)
    time.sleep(0.4)
time.sleep(1)

while True:
    # Play randomly
    for count in range(random.randrange(10)):
        chime.strike(random.choice(chime.scale), 1)
        time.sleep(random.randrange(1, 3) * 0.6)

    time.sleep(random.randrange(1, 10) * 0.5)

The Chime class was also used for an IoT Weather Chime project using the ESB32-S2 that plays "windless" electronic chimes in accordance with the outdoor wind speed: https://github.com/CedarGroveStudios/Weather_Chimes

API documentation for this library can be found in Cedargrove_Chime_API.

Attribution: Patch Symbols from PATCH & TWEAK by Kim Bjørn and Chris Meyer, published by Bjooks, are licensed under Creative Commons CC BY-ND 4.0. Some Patch Symbols were modified to create the synthio symbols BlockInput, MixerVoice, Note, Synthesizer, sample, and voice.

For additional detail about synthio diagrams, see Symbols for synthio Objects

• Limit the practical chime overtones to a specified frequency range such as 300Hz to 3000Hz.
• Provide additional chime scales.
• Update the Overtones class to include aluminum, wood, and brass.

• Lee Hite, 'Tubular Bell Chimes Design Handbook' for the analysis of tubular chime physics and overtones.
• C. McKenzie, T. Schweisinger, and J. Wagner, 'A Mechanical Engineering Laboratory Experiment to Investigate the Frequency Analysis of Bells and Chimes with Assessment' for the analysis of bell overtones.
• Liz Clark, 'Circle of Fifths Euclidean Synth with synthio and CircuitPython' Adafruit Learning Guide for the waveform and noise methods.
• Todd Kurt for fundamentally essential synthio hints, tricks, and examples (https://github.com/todbot/circuitpython-synthio-tricks).

Also, special thanks to Jeff Epler and Adafruit for the comprehensive design and implementation of the amazing CircuitPython synthio module.