I had a problem where a pianist had the choice to either use a lame piano or an electronic kepboard and opted for the keyboard. I was asked to record this performance which was in a church to raise funds for an overseas charity. I agreed but worried about how to make it "not mono." The sound was coming from an ordinary speaker; distinctly mono. Norsehorse came to the rescue with the suggestion that I use a "Center Ambient" method, new to me. Simply put it invlolved gaff taping an omni mic under the keyboard with the mic diaphragm about halfway between the center and edge of the speaker. The trick is with the second mic. It too is an omni, and was about six feet from the keyboard, further back on the stage and about four feet up.
I recorded the two tracks and approximately the same level. Following Norsehorse's instructions I used the omni under the keyboard as the center channel, duped the other omni, the "ambient" mic so I had two, panned one hard left, the other hard right and flipped the phase on the right channel.
When played back the two channels indicate in the level meter they are unique and separate, the Vectorscope in SAM shows a solid stereo image and when the track is played it sounds stereo. And like MS it sounds fine in mono as then just the center omni is heard.
At tip of the hat to Norsehorse for 1) knowing and 2) sharing. This is what makes GS Remote a great forum. And the artist was quite pleased, too. And she raised more money than she expected. No, the album will not be released to BMG.
But I have uploaded a short track so those who do not know about this can hear how it sounds.