LAME (LAME Ain't an MP3 Encoder) is a research project for learning about and improving MP3 encoding technology. LAME includes an MP3 encoding library, a simple frontend application, and other tools for sound analysis, as well as convenience tools. Please note that any commercial use (including distributing the LAME encoding engine in a free encoder) may require a patent license from Thomson Multimedia.
Mixxx is software for DJs that provides everything needed to create live mixes. It allows you to beatmatch songs and crossfade them together, like you would with turntables and a mixer. It runs without any extra hardware, and offers a wide range of advanced features including comprehensive MIDI controller and vinyl control support. To obtain the lowest latency and highest responsiveness, it uses hardware video acceleration and takes advantage of multi-core CPUs.
XMovie is a multimedia player for high quality Quicktime, MPEG, and DVD movies that supports 6 channel audio. The Quicktime decoder reads OpenDivx, assorted YUV formats, JPEG photo, MJPA, RGB, DV, IMA4, ULAW, Vorbis, and PCM codecs. The MPEG decoder reads MPEG-1 video, MPEG-2 video, MPEG-1 system streams, MPEG-2 system streams, VOB files, IFO files, MP2 and MP3 audio, and AC3 audio.
SoX is the Swiss Army knife of sound processing tools: it can convert sound files between many different file formats and audio devices, and can apply many sound effects and transformations, as well as doing basic analysis and providing input to more capable analysis and plotting tools.
m9u is a music server, similar to mpd or xmms2. It sits in the background, waiting for commands to be delivered via a 9p file system. m9u embraces the Unix philosophy of doing one thing well. As such, it does not try to catalog or otherwise organize music, but aims for the more humble goal of simply playing it. A side effect of this approach is that m9u is trivially extensible to domains aside from music (for example, an image slideshow).
Decibel is a GTK+ audio player designed for GNU/Linux. It aims at being very straightforward to use by means of a very clean and user-friendly interface. It aims also at being a real audio player and, as such, it does not include features that are not meant to be part of an audio player.
Sfront compiles MPEG 4 Structured Audio (MP4-SA) programs into efficient C programs that generate audio when executed. MP4-SA is a standard for normative algorithmic sound, which combines an audio signal processing language (SAOL) with score languages (MIDI and SASL). Under Mac OS X and Linux, sfront supports real-time, low-latency audio input/output and MIDI input. Under Mac OS X, sfront supports the creation of AudioUnit plug-ins. The documentation includes a book about SAOL programming.