odd the midifile issues doest crash for me either: I boot aquamacs
(leopard/intel), do M-x: cm and then eval this from the buffer
(define (testy n lb ub)
(process repeat n
do (send "mp:midi" (elapsed #t) .5
(between 50 90))
(wait .2)))
(sprout (testy 1000 60 90) "~/test.mid")
ive tried 10000 notes several times too, it works but takes about 2
seconds.