I have a song posted at YouTube that I recorded with my Boss BR-600 using two guitar parts (nylon strings), a bass, and four-part harmony. It comes from way back in the 1940s--the big-band era.

To create the master mix, I figured that the most critical part (easiest to mess up) was the harmony backup vocals, so I turned down everything except them, and adjusted them so I could hear each part. Then I brought up the lead vocal until it stands out just a bit. Next I turned up the rhythm guitar so it filled the piece, then the bass and lead guitar (solo and some fill notes in the second bridge).  

http://www.youtube.com/watch?v=cyeeGvwPV6E

I'm interested in hearing what others are doing, too.