Ruby noobie, midi generator toy

Hi, I’ve been playing with Rails for a bit, still pretty new to Ruby
itself, wrote something nifty and would be interested in feedback.

http://www.gilesgoatboy.org/ruby/midi.html

This is a simple file for generating music semi-randomly. The result
basically sounds like R2D2 meets Aphex Twin. It uses continuations
code from Hal F.'s book “The Ruby Way” and was partly written as a
way to learn more about continuations.