If you check out a guitar and a piano they are both the same. Both have a tunable string stretched between two points. In the guitar the sound board is the flat front of the guitar where the bridge is mounted, in a piano there is a sound board below the strings serving the same purpose. The sound actually varies depending at which point you place the microphone, so that the sound near the bridge end is different from the sound in the middle of the string:
These three different mike positions all present a different aspect of the sound.
The way the string is vibrated or striking method - also determines how it will sound.
Either way, the three positions of miking it will always apply.
the different pages from the index list above and