... I just forgetten about this.. but now it's back to haunt me. Reaper needs a mouseless "Toggle exclusive solo for selected track button" button . Seriously. It's been really cumbersome when comparing mixes to reference tracks. Imagine the usefulness of "Toggle exclusive solo for selected track button" buton, Track 1 is reference, Track 2 is your mix exported as stereo mix. Hit page up (track selection) , it automatically solo's Track 1, page down , it automatically unsolo Track 1, and solo's Track 2. Want to hear both ? Shift + Page Up/Down (select multiple tracks) . Simple.