struct midi_track {
  u8 type[4] | matches('MTrk') str;
  u32 length;
  u8 data[length];
};

struct midi {
  u8 type[4] | matches('MThd') str;
  u32 length | matches(6);
  u16 format;
  u16 track_count;
  u16 division;
  struct midi_track tracks[track_count];
};