This is THE quick fix for using your MIDI files in Ubuntu. It had frustrated me that all of the bug-reports about Totem not playing MIDI were ignored and shut down in Launchpad without much explanation other than installing Timidity. This is because the error is in Nautilus for Ubuntu presuming that MIDI is supported by default. It is not.

To get it working for now in Totem you have to install the Timidity package along with its extras and daemon. There is another recommended package in Synaptic, it is a good choice to install it too.

Hopefully those still having trouble reliving their 90s midi memories can be served by this brief explanation that covers what Launchpad ignored. Also, go file another bug report about nautilus opening totem for incompatible files, for fun.