OK! For some reason noatun was set to open as the default midi player. It seems I already had kmid so I've tried getting this to work but I get the error message "Could not open /dev/sequencer. Probably there is another program using it."
I can't detect any program running that would prevent this. Furthermore I don't seem to have a /dev/sequencer in my /dev directory.
I have installed Rosegarden to see if this would install its own sequencer but this won't work either.
Can someone advise me or point me in the right direction. I haven't had this problem before.