Java

FreeMusicPlayer - Part Java part native, supports MP3, WAV, Ogg, and playlists. Windows 2000/XP.

FreeTTS Speech Synthesizer - Written in Java, based upon Flite 1.1: a run-time speech synthesis engine from Carnegie Mellon. Open source, BSD.

Frinika - Cross-platform music studio software written in Java. Includes sequencer, software synths and realtime effects.

JavaTuner - Tunings and temperaments. Demo applet.

JavaZoom - Java MP3 Player supports WAV, AU, AIFF, Ogg Vorbis also.

JFugue - API for specifying music using simple strings and easily transforming patterns of music.

jOggPlayer - Gui Enhanced Vorbis Ogg Player. Freeware.

Neuralsemantics Modulator Jane - Applet uses standard AU sound files to modulate graphics on web page. Also offers Neurosonic e-Guitar.

RPitch - Relative pitch ear training to recognize intervals. Freeware.

SoftSynth.com - Music and synthesis software API, including JSyn and JavaSonics ListenUp.