Comment 6 for bug 210472

I believe this is because TiMidity is loaded prior to the Pulseaudio sound server.

I fixed this problem by restarting the timidity session: sudo /etc/init.d/timidity restart

After that, all MIDI-out wavemapping worked perfectly, and my program (in my case, Sibelius 4.x) did not steal focus from Firefox/emesene/etc

Give that a try. It's a more elegant workaround and can be programmed into Timidity (to start later.. or something... I guess...)