The MIME types are
and the file extensions
Store a midi file in your home directory. Open Nautilus and right click in the midi file. Select "Open with" (other application) or in Properties go to "Open with". Select Timidity in /usr/bin. Appears the text:
Change it to
Now, every time you click in a midi file, timidity is going to play it.
You can use a similar procedure for *.kar (open karaoke) files.
Go to Edit Preferences Advance and in "System preferences" mark the box "Use the system preferences" (if you have ?timidity installed in your Gnome system).
wiki:Self:PyKaraoke MIDI/CDG Karaoke player for Linux