A short read but one that provides some interesting notes (and possible starting points) for recording a piano. It also provides a concise and clear description of the piano's construction and mechanisms, though it does get a bit technical regarding tuning:
"For the equal temperament scale, the frequency of each note in the chromatic scale is related to the frequency of the notes next to it by a factor of 1.059463 ( or the twelfth root of 2 ) The twelfth root of two, when multiplied by the frequency of a note, gives the frequency of the next note up. After doing this for twelve notes, you end up with twice the frequency, or one octave up from the starting note and in twelve equal intervals. In equal temperament, A-flat and G-sharp are the same black key on the piano. This means that a composition written in one key can be shifted up any number of half steps (transposed) and will still contain exactly the same harmony, although the frequencies themselves will be different.
The Just or “harmonic” scale” however has each note related to the fundamental frequency by rational numbers with the semi-tones not equally spaced. Unfortunately this tuning depends heavily on the scale you are using and it is not possible to transpose from one key to another and produce the same harmony. This tuning is common for ensemble choral and orchestral groups who match pitch by ear."
As regards recording technique, the author notes that: "Some of the best classical recordings have been made using an A-B stereo pair placed on the side of the piano. Adjusting the distance to the piano and next to the piano, the amount of ambience and the timbre of the instrument can be tuned. Place the pair mid of the piano about 1 to 2 meters away with the microphones spaced 40 to 60 cm apart and adjust the stereo image so the pianist is to the left. The height of the stereo boom is at 1.2 m to 1.5 m above the piano. By pointing the microphones to the open lid of the piano, the sound reflecting on the inner side of the lid will be brightened giving depth to the recording. An incident pair of ambient room microphones can be added."
If you want to know more, you can check it out here.