"... intentionally in some of the older generation karaoke machines - they reverse the phase on a commercial recording and try to cancel out the lead vocal in a song!"

I didn't know that Dick!

Seems to be a rather clumsy way to remove voice from a recording, as there's also quite a bit of music in the same frequency ranges.

It'd also absolutely kill the low frequencies. I suppose you could compensate for that by using additional speakers wired in phase with a low pass crossover.

I frequently get calls from people wondering why they get good bass when playing music through just the left or just the right channel, but no bass when playing through both. I have to explain wave cancellation and the resulting acoustic vacuum it creates. Acoustical physics is a strange animal sometimes.

Bob (chip guy, car guy and speaker guy)