Python synthesizer

A simple virtual analog synthesizer written in Python.

• Oscillators: sine, sawtooth, square (with pulse width), triangle and noise, plus a detunable second oscillator
• ADSR envelope
• Resonant lowpass / highpass / bandpass filter
• LFO for vibrato, tremolo and filter cutoff modulation
• Playback via PyAudio and export to wav files

Installation

pip install synthesizer

To play sounds with Player, install PyAudio as well.

pip install "synthesizer[audio]"

Install dependencies for PyAudio

Ubuntu

apt install portaudio19-dev

macOS

brew install portaudio

Basic usage

Play 440Hz sine wave

Generated waves are NumPy arrays normalized to [-1.0, 1.0]. Available waveforms are Waveform.sine, Waveform.sawtooth, Waveform.square, Waveform.triangle and Waveform.noise.

>>> from synthesizer import Player, Synthesizer, Waveform


>>> player = Player()
>>> player.open_stream()
>>> synthesizer = Synthesizer(osc1_waveform=Waveform.sine, osc1_volume=1.0, use_osc2=False)
# Play A4
>>> player.play_wave(synthesizer.generate_constant_wave(440.0, 3.0))

Play chord

# Play C major
>>> chord = ["C3", "E3", "G3"]
>>> player.play_wave(synthesizer.generate_chord(chord, 3.0))

# You can also specify frequencies to play just intonation
>>> chord = [440.0, 550.0, 660.0]
>>> player.play_wave(synthesizer.generate_chord(chord, 3.0))

You can use PyChord to handle chords easily.

>>> from pychord import Chord
>>> chord = Chord("Dm7/G")
>>> player.play_wave(synthesizer.generate_chord(chord.components_with_pitch(root_pitch=3), 3.0))

Noise, pulse width and detune

# White noise (pass seed to make it reproducible)
>>> synthesizer = Synthesizer(osc1_waveform=Waveform.noise, seed=42)

# Square wave with 25% duty cycle
>>> synthesizer = Synthesizer(osc1_waveform=Waveform.square, osc1_pulse_width=0.25)

# Detune oscillator 2 by +7 cents for a thicker sound
>>> synthesizer = Synthesizer(osc1_waveform=Waveform.sawtooth, use_osc2=True,
...                           osc2_waveform=Waveform.sawtooth, osc2_volume=1.0,
...                           osc2_freq_transpose=1.0, osc2_detune=7.0)

ADSR envelope

Each generated wave fades in and out (10 ms by default) to prevent click noise between notes. The release is included in the length of the wave.

>>> synthesizer = Synthesizer(osc1_waveform=Waveform.sine, attack=0.05, release=0.2)
# Disable the envelope
>>> synthesizer = Synthesizer(osc1_waveform=Waveform.sine, attack=0.0, release=0.0)

Use decay and sustain for a full ADSR envelope, e.g. a plucked sound.

>>> synthesizer = Synthesizer(osc1_waveform=Waveform.sawtooth,
...                           attack=0.005, decay=0.3, sustain=0.2, release=0.1)

Filter

A resonant 2-pole (12 dB/oct) filter can be applied to the oscillators. filter_resonance is the Q factor; values above 0.707 emphasize the cutoff frequency.

>>> from synthesizer import FilterType
>>> synthesizer = Synthesizer(osc1_waveform=Waveform.sawtooth,
...                           filter_type=FilterType.lowpass, filter_cutoff=800.0, filter_resonance=4.0)

Available filter types are FilterType.lowpass, FilterType.highpass and FilterType.bandpass. High resonance may push the wave beyond [-1.0, 1.0]; such samples are clipped when played or written.

LFO

An LFO (low frequency oscillator) can modulate pitch (vibrato), amplitude (tremolo) and filter cutoff. Each depth is 0 (disabled) by default.

# Vibrato of +-30 cents and tremolo at 6 Hz
>>> synthesizer = Synthesizer(osc1_waveform=Waveform.triangle,
...                           lfo_rate=6.0, lfo_pitch_depth=30.0, lfo_amp_depth=0.4)

# Wah effect: sweep the cutoff +-2 octaves at 2 Hz
>>> synthesizer = Synthesizer(osc1_waveform=Waveform.sawtooth, osc1_volume=0.4,
...                           filter_type=FilterType.lowpass, filter_cutoff=800.0, filter_resonance=6.0,
...                           lfo_rate=2.0, lfo_cutoff_depth=2.0)

lfo_waveform accepts any Waveform; Waveform.noise gives a random value per LFO cycle (sample and hold).

Specify audio device

>>> player.enumerate_device()
# index: 00, name: "Built-in Microphone", rate: 44100
# index: 01, name: "Built-in Output", rate: 44100
# index: 02, name: "UA-25EX 44.1kHz", rate: 44100
>>> player.open_stream(device_name="UA-25EX")

Player can also be used as a context manager, which closes the stream and releases PyAudio resources on exit.

>>> with Player() as player:
...     player.open_stream()
...     player.play_wave(synthesizer.generate_constant_wave("A4", 1.0))

Write wav file

>>> from synthesizer import Writer
>>> writer = Writer()

>>> chord = ["C4", "E4", "G4"]
>>> wave = synthesizer.generate_chord(chord, 3.0)
>>> writer.write_wave("path/to/your.wav", wave)

# Concatenate multiple waves into a single file
>>> writer.write_waves("path/to/your.wav", wave1, wave2, wave3)

Examples

play_440hz.py

Play 440Hz waves with each waveform and some oscillator combinations.

python example/play_440hz.py

play_chord.py

Play various chords and a chord sequence.

python example/play_chord.py

write_wave.py

Write a chord progression to example/test.wav.

python example/write_wave.py

play_pychord.py

Play chords using PyChord.

pip install "pychord>=0.5.0"
python example/play_pychord.py A C#m7 DM7 Bm7/E A

play_synth_features.py

Play presets using oscillator extensions, ADSR envelope, filter and LFO.

python example/play_synth_features.py

Development

pip install -e ".[test,audio]"
pytest

Supported OS

• macOS
• Linux

Supported versions

• Python 3.10 and above

Author

• Yuma Mihira

License

• MIT License

Links

• PyPI: https://pypi.org/project/synthesizer/
• GitHub: https://github.com/yuma-m/synthesizer
• Documentation: https://synthesizer.readthedocs.io