VSTPLANET : VST Plugins Free - Virtual instruments and effects
Borderlands : The instrument may be performed by creating and destroying new clouds and dynamically moving them around the landscape. The landscape itself may also ...
Essentia : Open-source library and tools for audio and music analysis, description and synthesis
Band.js : An interface for the Web Audio API that supports rhythms, multiple instruments, repeating sections, and complex time signatures.
meSpeak.js : meSpeak.js (modulary enhanced speak.js) is a 100% client-side JavaScript text-to-speech library