Flues Synth
tl;dr I built a sound synthesizer that runs on a Raspberry Pi
The GitHub repo flues contains most of my recent synth experiments (various platforms, including live Web), the Raspi material is under flues-synth.
There are binaries of the Raspi synth and builds from Ubuntu of the lv2 plugins in the repo, but these versions are untested (used Claude-authored scripts)- building from source definitely works.
What is Flues?
Flues (flues-synth) is an experimental polyphonic synth for the Raspberry Pi. It is designed to run headless, without a UI. Input comes from a USB MIDI adapter. Output comes from either the Pi's headphone jack or a USB audio interface (other sound outputs such as HDMI and I2C HATs should work, but these are untested). It runs comfortably on a Raspi 4 1GB, I haven't tested on anything else.
Internally the synth engine is composed of the following modules :
- Disyn oscillators - a collection of novel synthesis algorithms (related to FM)
- Stove physical modelling subsystem
- Chatterbox formant filter subsystem
- Simple AR envelope
The flues-synth README.md has more details. There are live Web versions of the different subsystems that give an idea of the kind of sounds available.
A set of MIDI Programs provide various configurations of the modules, essentially presets. The parameters of these may be controlled using MIDI CC messages. Each Program exposes 9 core channels which may, for convenience, be mapped to external controllers using the flues-control lv2 plugin in a DAW.
(There are 9 channels because that's how many worked on my old MK-449 keyboard. I have since started using the sliders of an Akai Midimix for the purpose, via flues-control).
There is also a browser-based UI set up to supply control messages but this hasn't been maintained beyond its use in initial experiments.
Parameters are controlled by MIDI CC messages.
What Didn't Work
What I actually wanted initially, what led me here, was a Eurorack module that could do physical modelling synthesis. It's a paradigm that really appeals to me, not only because it can make realistic instrument sounds, but because it can make sounds that no physical object could have created. I couldn't find a module that was affordable, so decided to make one. Long story short, so far I've made a total pig's ear of the hardware side. Mistakes in ordering components, mistakes in fabrication decisions, etc etc. To be continued...