Staves and voices not played to MIDI output correctly

[lgvr123]

Issue type

General playback bug

Bug description

Since MU4, it is no longer possible to select to which MIDI channel an instrument must be played. And MU4's internal configuration is therefore not configurable by the user.

Two issues results from that : 1/ One can at least expect that all the voices of a same staff being played to the same channel. This is not the case. E.g. the voice 2 is not played on the same channel as the voice 1, leading that voice not being heard on the MIDI receiver.

2/ All the instruments are played on the same channel, where one could expect that every staff being sent to a separated channel.

Steps to reproduce

For Issue (1)

1. Create a score with 1 staff
2. Add a few note on the voice 1, add a few notes on voice 2
3. Connect a MIDI receiver and configure MU4's midi output to that receiver
4. Configure your MIDI receiver's input to only channel 1
5. Play the score in MU4

Expected : All the notes are heard whether on voice 1 or voice 2

Actual: Only the notes on voice 1 are heard not the ones on voice 2

For Issue (2)

1. Create a score with 2 staves
2. Add a few note on the staff 1, add a few notes on the staff 2
3. Connect a MIDI receiver and configure MU4's midi output to that receiver
4. Configure your MIDI receiver's input to only channel 1
5. Play the score in MU4

Expected : Only the staff 1 is heard not the staff 2

Actual: Both staves are heard.

Screenshots/Screen recordings

No response

MuseScore Version

4.02

Regression

Yes, this used to work in MuseScore 3.x and now is broken

Operating system

Windows 10

Additional context

OS: Windows 10 Version 2009, Arch.: x86_64, MuseScore version (64-bit): 4.0.2-230651553, revision: github-musescore-musescore-dbe7c6d