Reworking the Mixer UI
Some improvements to the mixer would make it easier it use, as discussed in this thread: https://musescore.org/en/node/274818#comment-846775.
An 'expand' toggle button that will show/hide parts with multiple voices (such as violins). When expanded, each part is given it's own slot in the mixer, just as it is now. When not expanded. a singe slot will control all the voices. So changing the volume of the 'Violin' will set the same value for the 'strings-tremolo' and 'strings-pizzicato' too.
Only the volume, pan, solo, mute and instrument name are shown on the main slider. Everything else is moved over to a 'details' panel. Clicking on a track will select it. When a mixer track is selected, the details panel will be loaded with the co-responding data to allow the user finer control.
Users will be able to assign a color to each part. This simply affects display and is for helping users keep track of the different parts.
A splitter panel will be used to separate the track side form the detail side so the user will be able to click and drag to resize the windows..