TiMidity++ is a software synthesizer.  It can play MIDI files by converting
them into PCM waveform data or other various audio file formats.

TiMidity++ can also be run as an ALSA sequencer client.  To do this, make
/etc/rc.d/rc.timidity executable and add this line to /etc/rc.d/rc.local:

/etc/rc.d/rc.timidity start

You will need a set of instrument patch files for TiMidity++ to be of any
use.  The freepats and eawpats packages, also available at SlackBuilds.org,
both provide a set of patch files.