Hi, almost four months later (as always) from the last comment, but I own a pair of very old M221 with their original AC401K and a pair of CMC6 w/ cardioid capsule.
They are night and day. The CMC6's are the most detailed microphones in my locker -and I do own a lot of mikes- but the 221's are the softest ones, so to speak. It has probably a lot to do with the fact they are very old, in fact their power supply is dying very fast, but I have never been able to record a viola with any other microphone the way the M221s capture its sound. They are smooth, full, but not very detailed, which sometimes is great in my experience. I prefer their omni position, to round even more the harshness of some instruments.
If the M222 -which I don't know- are capable of retaining this velvet and add clarity they are the best microphones which I can think about for anything.
Some of the best sounding classical recordings -very argueable- are made with M221's, like Ravel's Bolero by the Minnesota Orchestra/Stanislaw Skrowaczewski. It's a famous recording among purists.
BTW, If someone knows how I can repair my power supply (the same for both microphones) I will thank him/her a lot, as I am not very wealthy now to buy two new power supplies from Elvo/Schoeps.
Thanks and excuse my English.