Hi, I'm an independent music producer with an interest in R&D.
For background on this question, here is a helpful article on stereo panning. Stereo panning is used to give the sensation that a sound or instrument is coming from a particular direction, left, center, or right. Through adjustment of panning in a digital audio workstation or mix console, the listener can hear all of the instruments clearly even when there is a full band. By contrast, with mono sound, all the sounds come out of both sides of the system and seem like they are on top of each other. This is one reason stereo is such a vast improvement.
Anyway, in a typical mix console, there are potentiometers that control left and right panning. Here is a picture of a classic Solid State Logic 4000 G analogue console:
Interesting effects are possible when you double the instrument and pan one copy hard left and one copy hard right, or some combination of that. This produces a sensation of "width" where the sound seems wider than a normal instrument.
I am wondering whether anyone has used Mathematica to analyze panning and the perceived width of sound in stereo mixes. If not, I think it would be an awesome use of the program. For my first act, I would compute panning and width of different mixes of the same work to see what listeners respond to the best. That also seems like a possible research opportunity.