Playing standard music inbetween karaoke songs

I think the only thing missing at the moment from QMidi is the ability to play ordinary music and being able to fade this in and out (inbetween people singing karaoke songs played by QMidi). At the moment I use Quicktime to play a mix track of about 2 hours of standard music tracks and use Quicktime volume slider and stop button to do this. Can't we have a 2 slider setup in QMidi to achieve this?