If I'm reading correctly, you have a house mixer and you are feeding that signal to your Yamaha recorder? Are you sending the main outs from the house mixer? I don't know off the top of my head how many channels the Yamaha will record at a time, but if your other mixer has group outs, you could assign the music to a pair of group outs(for stereo) and then assign the vocals to another pair of group outs. If you want the ability to manipulate vocals individually, you could use a direct out or insert for that particular channel and feed that to the Yamaha on its own channel. I hope this helps.