Percussion and delta-time?

Hi list.

I'm experimenting with automated music composition in a bid to stop
contracting my soul to MegaCorp, and so it was a boon to find at last MIDI
in my fave language.

The documentation doesn't make much sense to me, though, specifically:

1. how can I get percussion?  Changing the channel to ten doesn't seem to do
the trick: is this my lack of MIDI or lack of Perl MIDI::*?

2. what is MIDI::Event's *dtime* or delta-time ?

Many thanks in anticipation,
lee