To the best of my knowledge, this is a rather unusual microphone technique for piano. Two figure-8 ribbon mics are placed equidistant from the center of the piano – one facing down from above and the other facing across the strings from the side. Mics are panned hard left and right, and because the figure-8 patterns are picking up and rejecting in opposite planes from each other the result is a very spacious stereo image. The lid must be removed for this to work well. To hear another example of this technique, listen to Todd E. Hill on iTunes.
Brian Ciach Fugue