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.
libgaudio is a C/C++ library to facilitate easy incorporation of sound and sound effects into games. Samples are loaded into memory and playback is then triggered or stopped. The system mixes any number of concurrently playing samples together (up to a predefined maximum). It is also possible to include a background MP3 soundfile in the mix.
libSap is linux port of windows' SAP Library which is a software emulation of CPU 6502 microprocessor and Pokey chip. Those two chips are used in Atari XL/XE computers. SAP Library is used to run programs written in 6502 machine language that are using the Pokey chip to play tunes and sounds.
PLIB is a set of libraries to write games and other realtime interactive applications that are 100% portable across a wide range of hardware and operating systems. It's used by Majik3D, FlightGear, and others, and includes libraries for GUI widgets, sound replay, geometry, scene graph, joystick, and fonts/text.