[MU4 Issue] unable to specify fretless electric bass sound

[MarcSabatella]

Describe the bug Although fretless electric bass is listed as an instrument, it does not play using the fretless sound, and no facility is provided to use this sound

To Reproduce Steps to reproduce the behavior:

1. Create new score
2. Choose Fretless Electric Bass instrumentt
3. Add some notes
4. Play

Result

Playback uses a standard fretted electric bass sound

Expected behavior

Playback should use the fretless sound

Platform information

• OS: Linux

Additional context This should work right out of the box upon selecting the Fretless Electric Bass instrument, independently of any concern over how one might choose between sounds in the mixer, since a fretless bass is a different instrument from a fretted one in a real sense. But, I do note again, the inability to select sounds in the mixer is by far the single biggest regression in all of MU4 to my mind. If you add an electric bass, there no way to choose from the various different bass sounds in your SoundFont (eg, picked vs fingered vs slapped). And picked bass is not a different instrument from fingered bass, so it's silly to try to solve this by listing them as separate instrument.