#microtonal #midi #modular #piano #synthesizer

app microwave

Make xenharmonic music and explore musical tunings

23 breaking releases

new 0.24.0 Oct 8, 2021
0.23.0 Jun 11, 2021
0.22.0 May 22, 2021
0.19.1 Mar 31, 2021
0.7.1 Jul 26, 2020

#48 in Audio

Download history 1/week @ 2021-06-25 4/week @ 2021-07-02 2/week @ 2021-07-09 30/week @ 2021-07-16 88/week @ 2021-07-30 3/week @ 2021-08-06 43/week @ 2021-08-13 2/week @ 2021-08-27 1/week @ 2021-09-03 1/week @ 2021-09-10 3/week @ 2021-09-17 1/week @ 2021-09-24 30/week @ 2021-10-01 49/week @ 2021-10-08

68 downloads per month

MIT and LGPL-2.1

14K SLoC

Make xenharmonic music and explore musical tunings.



microwave is a microtonal modular waveform synthesizer with soundfont rendering capabilities based on:

It features a virtual piano UI enabling you to play polyphonic microtonal melodies with your touch screen, computer keyboard, MIDI keyboard or mouse. The UI provides information about pitches and just intervals in custom tuning systems.


Download / Installation

You can download a precompiled version of microwave from the Releases section or you can build a fresh binary from scratch using Cargo:

cargo install -f microwave

To build microwave additional dev dependencies required by Nannou might need to be installed. On the CI environment (Ubuntu 20.04 LTS) the following installation step is sufficient:

sudo apt install libxcb-composite0-dev libasound2-dev

To run microwave you need the appropriate runtime libraries for your graphics card. For me (Ubuntu 18.04 LTS) the following step worked:

sudo apt install libvulkan1 mesa-vulkan-drivers vulkan-utils

If this doesn't help or you don't use Ubuntu/apt try following these instructions.


microwave run                     # 12-EDO scale (default)
microwave run steps 1:22:2        # 22-EDO scale
microwave run import my_scale.scl # imported scale

This should spawn a window displaying a virtual keyboard. Use your touch screen, computer keyboard or mouse to play melodies on the virtual piano.

Soundfont Files

For playback of sampled sounds you need to provide the location of a soundfont file. The location can be set via the environment variable MICROWAVE_SF_LOC or the command line:

microwave run --sf-loc /usr/share/sounds/sf2/default-GM.sf2 steps 1:22:2

If you like to use compressed sf3 files you need to compile microwave with the sf3 feature enabled. Note that the startup will take significantly longer since the soundfont needs to be decompressed first.

Modular Synth – Create Your Own Waveforms

On startup, microwave tries to locate a waveforms file specified by the --wv-loc parameter or the MICROWAVE_WV_LOC environment variable. If no such file is found microwave will create a default waveforms file for you.

Let's have a look at an example clavinettish sounding waveform that I discovered by accident:

name: Funky Clavinet
envelope: Piano
  - Oscillator:
      kind: Sin
      frequency: WaveformPitch
      modulation: None
      out_buffer: 0
      out_level: 440.0
  - Oscillator:
      kind: Triangle
      frequency: WaveformPitch
      modulation: ByFrequency
      mod_buffer: 0
      out_buffer: 1
      out_level: 1.0
  - Filter:
      kind: HighPass2
          - WaveformPitch
          - Envelope:
              name: Piano
              from: 2.0
              to: 4.0
      quality: 5.0
      in_buffer: 1
      out_buffer: AudioOut
      out_level: 1.0

This waveform has three stages:

  1. Generate a sine wave with the waveform's nominal frequency F and an amplitude of 440. Write this waveform to buffer 0.
  2. Generate a triangle wave with frequency F and an amplitude of 1.0. Modulate the waveform's frequency (in Hz) sample-wise by the amount stored in buffer 0. Write the modulated waveform to buffer 1.
  3. Apply a second-order high-pass filter to the samples stored in buffer 1. The high-pass's resonance frequency is modulated by the envelope named Piano and ranges from 2F to 4F. Write the result to AudioOut.

To create your own waveforms use the default waveforms file as a starting point and try editing it by trial-and-error. Let microwave's error messages guide you to find valid configurations.

Live Interactions

You can live-control your waveforms with your mouse pointer or any MIDI Control Change messages source.

The following example stage defines a resonating low-pass filter whose resonance frequency can be controlled with a MIDI modulation wheel/lever from 0 to 10,000 Hz.

  kind: LowPass2
      controller: Modulation
      from: 0.0
      to: 10000.0
  quality: 5.0
  in_buffer: 0
  out_buffer: AudioOut
  out_level: 1.0

Feature List

  • Sound features
    • Built-in modular waveform synhesizer with physical modeling synhesis
      microwave run --wv-loc <waveforms-file-location> [scale-expression]
    • FluidLite soundfont renderer
      microwave run --sf-loc <soundfont-file-location> [scale-expression]
    • External synthesizer via MIDI-out
      microwave run --midi-out <midi-target> [scale-expression]
    • Microphone / aux input
      microwave run --audio-in [scale-expression]
    • WAV recording
  • Control features
    • Sequencer / piano keyboard via MIDI-in
      microwave run --midi-in <midi-source> [scale-expression]
    • Computer keyboard (configurable isomorphic layout)
    • Touch Screen
    • Mouse
    • Channel events (pitch-bend, modulation, pedals, aftertouch, etc.)
    • Polyphonic events (key pressure)
    • LF sources (envelopes, time slices, oscillators, etc.)
  • Effects
    • Low-pass
    • 2nd order low-pass
    • High-pass
    • 2nd order high-pass
    • Band-pass
    • Notch filter
    • All-pass
    • Reverb
    • Spatial delay
    • Rotary speaker
  • Microtuning features
    • Custom scales
    • SCL imports
    • KBM imports
    • Tuning-dependent automatic isomorphic keyboard layouts
    • Customizable second visual keyboard (--kb2 option)
    • MIDI-out retuning via Single Note Tuning messages
    • Display frequencies and rational number approximations


For a complete list of command line options run

microwave help


microwave statically links against fluidlite for soundfont renderering capabilities. This makes the binary executable of microwave a derivative work of fluidlite. fluidlite is licensed under the GNU Lesser General Public License, version 2.1.


~562K SLoC