Solo / Mute without opening Mixer
Does this actually exist? Not sure. But if not here's my idea:
When you select a measure or a note of a specific part you right-click and see on the small window that appears new buttons: Solo and Mute ... Obvious functions, and probably Mute won't be needed. BUT this will not act like the button in the mixer (which, when you have more than 1 parts of the same instrument ,it will let every part of the specific instrument be heard alone , which actually doesn't sound like solo...) but instead this "solo" button will mute every instrument except the specific part.
We could also have a second solo button which will open a second window which says which voice will be heard, (the first solo button which doesn't open a second window will allow all voices in the part/staff to be heard).