music library manager and MusicBrainz tagger

A JavaScript Sound API supporting MP3, MPEG4 and HTML5 audio + (experimental) RTMP, providing reliable cross-browser/platform audio control in as little as 10 KB. BSD licensed.

Play is an employee-powered iTunes-based client-driven distributed music server for your office.

An eight-volume set of organ accompaniments to the Nova Organi Harmonia Gregorian chant

A Javascript library for working with Audio. Features a simple interface as the front end to multiple audio APIs via a plugin model. Currently supports WebAudio, HTML5 Audio, & a Flash fallback.

Echo Nest Remix is the Internet Synthesizer. Make amazing things from music, automatically.
Turn any music or video into Python or JavaScript code.

This is an open and public initiative to bring more harmony into HTML5 Audio implementations. The specifications are missing some features and sometime leaves room for interpretation. We want to un-mute the Web and make Audio rock!

MuseScore is an open source and free music notation software. For support, contribution, bug reports, visit MuseScore.org. Fork and make pull requests!

Tomahawk, the social music player app (Qt / C++)

MusicBrainz Java data bindings using Hibernate

MusicBrainz Picard is a cross-platform (Linux/Mac OS X/Windows) application written in Python and is the official MusicBrainz tagger.

Picard supports the majority of audio file formats, is capable of using audio fingerprints (AcoustIDs), performing CD lookups and disc ID submissions, and it has excellent Unicode support.

These libraries for Python, PHP, Ruby, Node.js and Java implement the subset of OAuth that is required to talk to the Rdio service with minimal external dependencies.

This is a Spotify App that shows useful code snippets that can help you build Spotify Apps. With these examples you can build the next generation music mashup.

Making life easy to create a MIDI-app on the web. Includes a library to program synesthesia into your app for memory recognition or for creating trippy effects. Convert soundfonts for Guitar, Bass, Drums, ect. into code that can be read by the browser. Supports multiple simultaneous instruments and perfect timing.

cursynth is a polyphonic, MIDI enabled, subtractive synth that runs in your
terminal with an ascii interface.

cursynth will connect to all MIDI devices and send output to the default audio
device on your system.

A free and open platform giving all musicians access to tools that let them manage, promote, and sell their music online.

Mopidy is a music server which can play music both from multiple sources, like your local hard drive, radio streams, and from Spotify and SoundCloud. Searches combines results from all music sources, and you can mix tracks from all sources in your play queue. Your playlists from Spotify or SoundCloud are also available for use.