Pure Data - Pd (aka Pure Data) is a real-time graphical programming environment for audio, video, and graphical...
Google Open Source - All of Googles open source projects under a single umbrella
VCV Rack - A cross-platform modular synthesizer.
LaunchKit - Open Source - A popular suite of developer tools, now 100% open source.
SuperCollider - A real time audio synthesis engine, and an object-oriented programming language specialised for...
Open Source @IFTTT - A collection of IFTTT OSS projects.