There are a lot of good articles on the web as to why LCR is a mixing technique that can pay off a lot in a mix.
LCR Mixing Sucks
Building an Effective Mix
and whole ginormous threads on it at gearsluts and the womb.
I know some people have an idea that this is some ancient technique for old music, but it's constantly applied in the industry and you can hear it all the time if you listen to guys like Bruce Swedien's work over the years as well as many others.
I like these two articles because the first reflects some of how I approach things, e.g. not just being hard core LCR, but also filling in the rest of the spectrum, and the second because I was one of those idjits sitting there at the corner of Mass Ave and Boylston having arguments with other students about panning - I graduated when Dave came on board. :)
Since getting back into it and really taking advantage of the cool advances in things like spectrum widening and mid/side processing, I've fallen into a trap of not being as conscious about the mono mix as I should be.
Anton Wannemakers and I've been going round and round on this recently and he made a telling point the other day while discussing a mix we've both been having fun hacking at in a private proj, and that was that while you could accept certain compromises in a mix when you mono it, totally losing something like background vox due to the panning was over the line.
Grudgingly, I had to agree, lol...
But rather submit to the notion that this was intractable, I started thinking about the problem and tried to do some research (the interwebs really lack a lot of substance on this issue, as far as I can tell, and I'm usually pretty good at the googles....).
See, I love the separation LCR and panning in general can give a mix, and widening things out as well. So sacrificing that for mono compatibility was a hard pill to swallow.
As I thought about this it occurred to me that a solution might be to double each track and pan exactly opposite and to fool with the phase of things.
This yielded marginal results, better for mono, not so good for stereo. Yet I felt like I was on the right path and decided to try other ways to effect phase - and hit upon something that really seems to work.
If I dup the tracks, and pan them opposite, and then drop the dup'd tracks level -3db from the orig, I managed to have almost the same full rich LCR spectrum in my backing vox when in stereo, and in mono, they were just a tad softer than if they were all mono.
The idea sprang from reading Dave Mouton's article today and I have to say it's really been satisfying to figure out a way to address this issue.
I suppose this might have been obvious to some folks, but as it was a revelation to me today as a technique, I thought I'd share.
Thanks to Anton for being a cattle prod on the issue. :D