Mixere is a free, open-source application for mixing audio files. It runs on Windows NT/2000/XP, and supports WAV, AIFF, MP3, Ogg Vorbis, Flac, and Mod audio files.
Mixere is optimized for live performance, and especially for creating live sound collage. Conceptually, it's like a rack full of CD players connected to an automated mixer. Mixere's features include dynamic looping of audio, auto-triggering of audio, fully automated sliders, "soft" (gradual) mute/solo operations, crossfading between documents, snapshots, and unlimited undo.
A Mixere document consists of a number of tracks, each containing a single audio file. Any number of tracks can play simultaneously, subject only to the limits of Windows and sound card performance. Audio is streamed directly from disk, so there's no limit on audio file size, and no waiting for audio to be loaded into memory.
Mixere's interface is similar to a spreadsheet. The rows are tracks, and the columns are properties which can be adjusted for each track: name, transport (play/pause/stop/loop), mute/solo, volume, pan, pitch (+/- one octave), and audio position.
Mixere uses an open-source audio library called Audiere.