Need help with MIDI

[labelas@hotmail.com (Labelas Enoreth)]

Here is my problem...
I had some files which contained MIDI data, but without a standard header,
and I wanted to 'rip' this data out so I could listen to it whenever I
wanted to (and put one up on my webpage to play, but that's another story)
So I cut out the proper data and then made up a standard header for
it...and it worked...however, I have a problem. There is no timing
information so the music plays about 50 times too fast. Is there any
utility which will simply let me open up the MIDI file and change the
tempo and then resave it without having to import it into some special
non-MIDI format? It was originally from a IIgs, but I had to move
instruments around because of the odd mapping and compatibility, and I'm
afraid that if I do som ekind of import/export runaround it will get all
screwed up,