The Advanced Linux Sound Architecture (ALSA) is a Linux kernel component intended to provide device drivers for sound cards.
- Wikipedia:Advanced Linux Sound Architecture
The Open Sound System is an alternative sound architecture for Unix-like and POSIX-compatible systems. OSS version 3 was the original sound system for Linux and is in the kernel but was superceded by ALSA in 2002 when OSS version 4 became proprietary software. OSSv4 became free software again in 2007 when 4Front Technologies released its source code and provided it under the GPL license.
The Jack-Audio-Connection-Kit is a sound server for advanced use, and is generally used by professionals looking to record. Regardless it does support mixing, although to get non JACK aware applications to work, a plugin has to be provided. The alsa-plugins package will pull this in.
Also called JACK-mp, it is the next version of JACK, with support for multi-processors and for network audio.
- schedtool/nice (with sound server)