2004-07-05
  * Rests and Notes

  Rests and Notes are the sonic atoms in a Music,
  whereas the other constructors structure the Music.
  Sonic atoms share the property 'duration'
  but in the original design functions like 'perf'
  couldn't benefit from that.

2004-05-23
  constructor 'Sequence' instead of ':+:',
              'Parallel' instead of ':=:',
              implemented +:+ and =:= as replacement for these constructors
  '=:=' meant a meter change before, turned it into '=/='
  the optimization algorithms in ReadMidi are partially wrong
     or optimize too less or let me doubt about some the structures of Haskore

2004-05-22
  'div' instead of 'quot' for Note conversion
