ixi software : ixi audio is an experimental project concerned with the creation of digital musical instruments and environments for generative music.
Band.js : An interface for the Web Audio API that supports rhythms, multiple instruments, repeating sections, and complex time signatures.
Essentia : Open-source library and tools for audio and music analysis, description and synthesis
meSing.js : meSing.js is a JavaScript singing synthesis library that uses the Web Audio API's DSP capabilities in conjunction with the meSpeak.js speech synthesis...
librosa : librosa is a python package for music and audio analysis. It provides the building blocks necessary to create music information retrieval systems.
SoundCloud lets you move music fast & easy. The platform takes the daily hassle out of receiving, sending & distributing music for artists, record labels & other music professionals.