The Advanced Linux Sound Architecture is composed of several parts. The first is a fully modularized sound driver which supports module autoloading, devfs, isapnp autoconfiguration, and gives complete access to analog audio, digital audio, control, mixer, synthesizer, DSP, MIDI, and timer components of audio hardware. It also includes a fully-featured kernel-level sequencer, a full compatibility layer for OSS/Free applications, an object-oriented C library which covers and enhances the ALSA kernel driver functionality for applications (client/server, plugins, PCM sharing/multiplexing, PCM metering, etc.), an interactive configuration program for the driver, and some simple utilities for basic management.
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.
libxmp is a module player library which supports many mainstream and obscure module formats, including Protracker MOD, Scream Tracker III S3M, and Impulse Tracker IT. Possible applications for libxmp include standalone module players, module player plugins for other players, module information extractors, background music replayers for games and other applications, module-to-mp3 converters, etc.
The FAAC project includes the AAC encoder FAAC and decoder FAAD2. It supports several MPEG-4 object types (LC, Main, LTP, HE AAC, PS) and file formats (ADTS AAC, raw AAC, MP4), multichannel and gapless en/decoding as well as MP4 metadata tags. The codecs are compatible with standard-compliant audio applications using one or more of these profiles.
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.
libsndfile is a C library for reading and writing sound files such as AIFF, AU, WAV, and others through one standard interface. It can currently read/write 8, 16, 24 and 32-bit PCM files as well as 32 and 64-bit floating point WAV files and a number of compressed formats. It compiles and runs on *nix, MacOS, and Win32.
Beast is a powerful music composition and modular synthesis application. It offers multiple input methods like multitrack, piano roll, and pattern editing and supports skins. On the technical side, it has a wide range of abilities like sequencing, unlimited undo/redo history, real-time synthesis with multiprocessor support, full duplex 32-bit audio rendering, precise timing down to sample granularity, on demand loading of partial wave files, on the fly decoding of various sample formats, aliasing free oscillators, and full Scheme scripting support.