MIDI export: the first track should not contain note events
Musescore prepares type 1 (multi-track) MIDI files incorrectly.
1) Musescore assigns note events of the first Instrument (staff) to Track 0. This is wrong.
Track 0 is supposed to be a "conductor" track, which only includes the meta events: all meter and tempo changes. It is not supposed to include notes or other data. Instruments (staves) are supposed to be separated into tracks, starting with Track 1 (not Track 0).
2) Musescore needs to separate voices into separate channels per track. In other words, voices on the same staff should be assigned to separate MIDI channels in the same Track. Example: a bass clef which is the second clef in a grand staff should be Track 2, with tenor and bass voices assigned to channels 1 and 2 respectively.
The points above can be verified in the MIDI File specification, sections 2.2 and Appendix 2: http://www.cs.cmu.edu/~music/cmsip/readings/Standard-MIDI-file-format-u…