Morgan C
MAX LOUD PRESETS¯\(°_o)/¯
No, the idea is that you flip the phase on one of two monitors that are symmetrically placed so that they're bleeding into the vocal mic equally. When you flip the phase on one of them, they'll effectively cancel out at the mic, but the singer will still be able to hear them.
Can you also just record the song through with no singing, so you're just getting the backing mix through the mic, and then reverse the polarity of THAT after recording, and then mix it in with the recorded vocals? Now that I think about it it seems like a lot more work though..