I was reading something in the current ComputerMusic magazine about how to isolate vocals from a track, which might deliver something of what you are asking. However it didn't necessarily sound like something Music Maker might have the right tool set for, nor did I fully understand it. Something about overlaying two different versions, reversing the phase of one . . . . . . . and there it lost me.

However you can also go another route, which is to look at sites like Metapop.com, which runs competitions to remix tracks. It's looking a lot less active on that front recently, but keep an eye out there and you'll find downloadable stems, often including vocals to play with. Read the rules carefully though because copyright for the tracks and restrictions about how and where you put your remixes do apply. Splice runs similar things.