title: music21: parsing notes and durations per track
body: <p>I'm trying to use music21 to convert multi-track midi files into array of notes and durations per each track.</p>
  
  <p>For example, given a midi file test.mid with 16 tracks in it,</p>
  
  <p>I would like to get 16 arrays of tuples, consisting of (pitch, duration (plus maybe position of the note)).</p>
  
  <p>Documentation for music21 is rather difficult to follow, and I would really appreciate any help on this..</p>