[MU4 Task] Condensing Feature for Scores instead of using voices

[CombinedAtom]

It is an automated feature that condenses two parts into one part with all the voices there and automatically doesn't affect the individual parts. It is quite a pain if you only do it manually...

[oktophonie]

Discussion about this has been going on for a long time. (It's a huge and very difficult feature to properly implement, though.)

[Tantacrul]

We have a very large amount of planning to do - the most complex of which surrounds how we want to address our engraving engine, which is in need of a re-structuring and re-imagining.

A few features fall under this:

• Condensing scores
• A fully functional piano roll
• Proper divisi staves

It's too early to say anything decisively but my sense is that we should complete the needed re-structuring first in order to unlock these features so they can be maintained properly - and aren't just more hacks that end up grinding our development to a halt.