Xine is the name of a Free media player library (movies and audio). It comes with its own video player application, also called xine, but there are other programs that use the Xine engine, such as gxine, and oxine.
Xine can be made to use various codecs. By default, Xine will look for more codecs in the /usr/lib/win32 directory. One can find additional codecs at the mplayer website.
Unfortunately, xine doesn't have a decoder for midi and is unable to play the midi format.