MIDIOX has two functions MF2T and T2MF that will convert a midi file to text and
back. These are windows/dos command line programs that should work with wine.
I used it to edit cakewalk generated midi files with windows notepad when I was
first learning midi (before I switched to linux). The text files are easy to read and
edit if you understand the midi spec.
http://www.midiox.com/
I started converting emacs asm86mode into a midi file mode with little success,
but I still think it would be a good project.
-- Jeff Sandys