[Tom McCreadie]

Mike, I am surprised at your question. Everyone knows that if you reverse
the polarity of one of the two mono tracks and add them together you will
null them out. What you do is highlight just one channel and hit Invert
polarity and you get not two out of phase channels but rather two flat
lines. Isn't that what you would expect?

But you threw us off by not mentioning anything about 'and add them together' in
your original post.
--
Tom McCreadie