I’ve come to the M/S party very late.
I’m using the (free) Voxengo MSED plugin. It’s amazingly simple.
There are other plugins by Waves and UAD, etc, that are also out there.
The Brainworkx EQ V.3 for UAD looks stunning, but my older Mac won’t run it.
Basically, you can do anything you want to the main parts of
the mix (middle and two sides) including gain changes, adding EQ, FX,
compression. Of course it’s always going to be a matter of what
you want to achieve. Simply adding a bit of gain to the sides
results in a marvelous widening affect, let alone doing anything
else. A little bit seems to go a very long way.
If you were a mastering engineer, I can see why the technique
would be a regular (if not permanent) choice. I think I’m a
Luckily, the M/S party still has some booze left for me!