The extensible media player

Xmms is a media player for the X Window System that supports Winamp
skins and that has a sophisticated plugin system that allows for easy
extension of its abilities. Xmms is able to deal with all common types
of media files.

You might want to have a look at the xmms-plugins package which
contains a large number of effect, input, output, and visualization
plugins for xmms.