A cross-platform polyphonic synthesis library with MIDI support.
- Open in Qt Creator (4 or higher)
- Build
I've been fascinated with digital signal processing and real-time audio for a long time. I'm a musician, and wanted to combine my love of the piano with my understanding of C++. I'd heard of frameworks like JUCE, but wanted to try out a lower level approach. I owe the foundation of my ideas to this fantastic C++Now presentation by Timur Doumler.
Unfortunately std::audio is still in early stages, so I looked to portaudio for a more robust real-time audio callback.
The audio synthesis techniques demonstrated in this project can be attributed to The Audio Programming Book by Richard Boulanger and tutorials by Bela.
Midi input is handled by the RtMidi library.
- Wavetable oscillation that supports fill functions as lambdas. Wavetables are passed into the microtone::Synthesizer constructor with adjustable weights. This data is shared between the oscillators.
- Polyphony -- 127 voices, each wrapping an oscillator. This is probably overkill (try playing 127 notes at the same time!), but only active notes on the midi keyboard will trigger the voices
- Envelopes (Attack, Decay, Sustain, Release): The oscillators belonging to each voice conform to configurable envelopes. Without this, you'd hear clicks and pops when notes are released or pressed in rapid succession -- at least in continuous functions like sine waves. This also adds richness and character to the sound.
- Filters (low-pass, high-pass, etc).
- Forwarded audio buffers -- update your UI with live audio data by passing a lambda to the microtone::Synthesizer constructor.
- Midi input, including the sustain pedal.
Another dream of mine was to write a tiny synthesizer for use in the terminal. I thought it'd be neat to spin up a little executable instead of waiting on some heavy-weight DAW every time I wanted to play the piano.
A console application that manages an instance of microtone. It displays midi input and audio output through a piano roll and oscilloscope, and includes an envelope editor in a separate tab.
Microtone can be used for a lot more than what you see in asciiboard. If I find the time, I'd love to build Microtone into a larger API, one that I could use to create all sorts of interesting audio tools. For now it's just a synthesis API.