AMP is a command line mp3 player/decoder released under a BSD style license. This became the foundation of WinAmp. Winamp is 'the' mp3/audio player for Windows, and is said to no longer contain any remnants AMP source these days.
Some time after Winamp was released, it was cloned as 'x11amp' for *nix - which was again based on AMP. Winamp later got the x11amp folks to rename their player, and so it became 'xmms' (X MultiMedia System).
2 pages link to AMP:
