That M-S piano recording was incredible. I wouldn't have guessed ribbons.
Why wouldn't you? Have you heard condensers that smooth?
As I said earlier the M is a cardioid ribbon.
Here is another track from the same CD:
Thank you once again, Marik. Your impressive work speaks for itself; one rarely finds someone with a true understanding of classical piano sound. I am fortunate to have access to someone with such skills, so forgive me for bombarding you with some more questions–your generosity is much appreciated.
1. Why do you recommend the SP C4s, as opposed to other mics in the same price range?
'Cause I recorded with them and stock (unmodified) they worked quite well for the piano. Besides, they come in matched pair with set of omni capsules.
2. These are really inexpensive mics (~$400 a pair). This is great news, of course! But shall I assume, based on what you wrote, that spending up to an additional $600 on microphones would not significantly increase the potential recording quality? Could you give a couple of more examples of "classical piano-friendly" mics below $1000 in addition to the C4s?
Another my (absolute) budget favorite is a highly modified MXL603. Those are actually very interesting mics. The electronics are a famous Schoeps circuit (good copy), and the capsules are a copy of Neumann KM84. Stock, the mics lack some bass, but when modified they can sound quite amazing--very neutral, with excellent bass, flat response, etc.
Here is a recording done with those using ORTF. I have to say, this particular recording probably does not do them justice, as the recording conditions were awfull. It was an International Piano Competition and for esthetics reasons

they did not let me place the mics in front of the instrument, so they were some 20' on the side of the hall, close to a wall. Still, I think they represented the sound of Bosendorfer Imperial and its powerful bass quite faithfully:
3. Any recommendations for a ribbon microphone to partner with the C4s for MS recording?
For this one please contact me privately.
4. Considering the potential of the Apogee Duet interface, after what price level does microphone quality begin to be irrelevant? Is the interface too weak, for example, for an expensive microphone such as the AKG414B-XLS? Or the DPA 4050, which I can get for around $1000 a pair?
You see, your setup is only good as its weakest link. The use of interface for the recording by itself is already a weak link (no matter how good it is). But the weakest link as I see it (sorry to be brutally honest) is your 6' Yamaha and upright in a highly reverberant room. I just don't see much sense to suggest you getting Schoeps, DPA, or Josephson to record through interface in such conditions.
5. If I won the lottery and had up to $1,500-$2,000 to spend on mics, what mics would you suggest? Would you recommend the AKG 414B-XLS, for example?
Oh God, no. I tried those a few times and for piano they consistantly were horrable. In any case, with piano I prefer to stay small diaphragm mics, or ribbons.
IMO, if you ever win a lottery, treat yourself nicely--get a bigger piano--I never heard any small grands on recordings having a nice bass.
Best, M