When you press f5 you can change the volume of any track you want, at that bar. Or set it back to 'normal' which is what is was at the start.

So if you want to start with the solo track at 60, then change it to 85 at bar 17 you go to bar 17 with the cursor and press f5. Then you change the volumes of any track there. Any bar with a red marker in it has some sort of thing you can find using f5 including instrument changes.

Most people here, if they really wanted 3 soloists, would use Realband. Another bunch to learn, but it's easier to manage because you can have each of a different track.

John Conley
Musica est vita