As you get familiar with listening this way, you will begin to more easily pick out the separate strands of the A-B element and the musical tension and interest that their interaction with A+B creates. You will usually find there is an approximately equal balance in interest between A+B and A-B, even though the most central musical elements are usually in A+B.

You will notice the high-frequency rhythmic “framing" (often or usually A,B) that surrounds and supports the A+B music. This is usually equally balanced left and right, and is often doubled rhythm guitars, keyboards, and/or high-frequency percussion.

A-B parts often “answer" (as in harmony vocals) A+B parts (as in lead vocals). Sometimes, the line of musical interest “bounces” in and out, back and forth from A+B to A-B on alternating notes, beats or measures, giving an elastic spaciousness to the recording.

Finally, uncorrelated unisons panned Left and Right (so-called “doubling") have proved to be one of the most beautiful and powerful effects in multitrack recording, while out-of-polarity high-frequency signals panned Left and Right yield a powerful spatial ambiguity that contrasts strongly and effectively with the monaural Center image.

It will become apparent as you spend time listening to A-B that multi-track production does not often evoke the image of a concert stage (except for special effect), but rather has evolved into a particular and quite identifiable “loudspeaker music" style. This has happened in response to the realities of the various ways people listen to recordings, such normal living-room stereo, mono radios & TV, in cars, through boom-boxes, and over headphones. Music that sounds good over all of this array of different systems must be “mono-compatible” while also being interesting and entertaining stereo that is easily audible off the median plane. Music produced with an A+B/A-B approach, with its strong phantom image, strong A and B side components, and active spatial interplay, satisfies these requirements pretty thoroughly. The fact that it isn’t a realistic reproduction of a live performance is comparatively unimportant in pop/rock recording, because (a) pop music is created primarily for playback over loudspeakers and (b) the vast majority of artists and listeners listen primarily or exclusively to loudspeakers for their music. So, I recommend that you experiment aggressively with A+B/A-B to better take advantage of our medium. Consider using it as a primary production technique, right from the beginning, including in the way you compose, preproduce, score and record your music.

Happy reverb trails!