I specialize almost exclusively on classical piano recording and besides numerous live recordings, as a sound engineer so far have 6 commercial piano CDs, 4 in work, and 7 scheduled for the next year.
I had a pleasure working with some really big stars and beeing a concert pianist myself (as well), have a doctoral (abd) degree in piano performance (as well as MM from Moscow Conservatory)
Here is what I learnt so far:
1) There is no hall and no piano (at least I never met), which would require more than 2 mics to do the job right.
2) I can tell you for sure--if a classical pianist will hear a close miked recording, it might be your last day in business.
3) You should be carefull with omnies in live situation. Although they are the mics of choice for piano, with more projecting instruments you are forced to get to a more distant miking and have a danger of picking more noise from audience and AC. A pair of cardioid SDCs (although a compromize) would be a better idea here.
4) Don't do the miking just for sake of "what sounds good". The repertoire and individuality of the performer are as important (or even more). What is good for Bach or some contemporary composers won't suit Mozart. What is good for Mozart won't necessarily suit Rachmaninov or Scriabin. What is good for one performer can sound awfull with another. If all of those are performed in the same concert you should find a "middle way".
Only your artistic taste can tell you solution.
5) Some practical aspects:
If you want to make a good artistic piano recording (not the one most radios do, i.e. put the mics on familiar spot and press record botton), most important--get familiar with repertoire performed. Find CDs and listen to the music.
Come to the hall for a dress rehearsal. Listen from the hall, paying special attention to individual touch of the performer, use of pedal and dynamics, emotional involvement and connection with the music.
Go on stage, listen to the sound of instrument in different spots, paying attention to the sound in the hall (from the stage), then go back to the hall and listen from there.
Your artistic intuition should tell you what would be a sweet spot between piano/performer/hall/type of music/mic position relationship.
Here is one of the tracks I made a couple years ago for a commercial CD. Couple of SDCs omnies with Jecklin disk. Straight, unmastered track from the session, just edited for removing noises from reaching to the strings. Sorry for presenting MP3--my webspace is limited:
As a side note, usually I spend anywhere between 1 1/2 to 9 hours, just for the miking.
