[CM] tempo-change

[Rick Taube]

> creates in sibelius tempo 90000 or so.
> is this a problem of sib or is something wrong with my code?

the make-tempo-change function is a low-level function that expects its 
argument to be in micro-seconds (usecs), not beats-per-minute. So add:

(define (bpm->usecs bpm)
   (floor (* 1000000 (/ 60 bpm))))

then do:

 > (tempomsg (now) (bpm->usecs 120) )


also you can use the function 'midi-file-print' to print out the 
contents of your midifiles when you want to inspect raw midi values:

 > (midi-file-print "/whatever/foo.midi")