Updated - Movin to Sante Fe with Fruition - Mix 5

[Mixinthecloud]

While I agree with everything you've said so far MitC I would disagree that M/S is relatively new tech. Heck, it's part Alan Blumlein's stereo patent mentions the concept back into the 30s. The Fairchild 670 had the Lat/Vert option which is basically M/S compression. It's how vinyl records work.
Essentially anything that widens or narrows a stereo image is working on the principle of Middle Side sum and difference. Yes there are more plug ins taking advantage of M/S and the technique has grown in popularity but I believe it's due more to it being simpler and more efficient to implement in the digital world as opposed to the hoops one had to go through in the analog world. Decoding an M/S microphone alone without a matrix took up 3 channels then had to be bussed in stereo if you wanted to compress or eq the image. Though sometimes I would just compress the mid microphone signal though the results were never as dramatic as I hoped. There's a certain narrow zone where the interplay of mid and side signals work together to create a stereo image and by compressing too much I'd just get out of phase side signals as opposed to stereo. I didn't have as good a grasp on it as I do now.

I don't bother much now but you can M/S any stereo signal these days if you have a plugin that has an M/S matrix in it. I know it's in Logic. I'd reckon there must be a free one out there for any platform. Just put on the matrix to split the signal into Mid and Side, any plugin you'd like to process and then the matrix again to decode it back to stereo.

Sorry that's a lot of words and I hope I'm fairly correct in what I'm mentioning. I've just long been fascinated with M/S and sometimes it comes across as 'voodoo' to some people (not saying you) and I've had people argue that it isn't even stereo. M/S with a cardioid pattern microphone is mathematically the same as XY depending of the ratios of mid and side pattern.

I'm sure you know all this but maybe someone else will happen upon it and find it interesting.

My statement on the newness of M/S processing is only a reaction to the inclusion of it in just about every plugin these days. In the analogue world in which we grew up, M/S was not an easy get and took a lot of patching to accomplish.