Miking the piano to present a crystal clear performance can be a bit tricky. It is best have two people work on this setup, so find an assistant if you can. Also, you may want to work closely with the sound tech on this and ask them to mark the settings after you get the clear, full sound that you are looking for.
Every piano is different in many ways. They have different shapes, different age strings, different cabinets, etc. Some pianos have new bass strings which are loud and bright, while others have older strings which are usually quieter and sometimes present a "tubby" or short sustain sound. Plan your time wisely when miking your piano.
Miking the Grand Piano (in stereo if possible)
First, lift the lid and prop it up with the longer stick. Grab two mic stands equipped with booms and place the first mic about 12 inches above the bass strings. Now, aim the mic at the string in the middle of the bass range at a point about halfway down the string.
Now place the second mic about 12 inches away from the middle of the treble string set and about halfway down the length of the strings.
Set the bass strings' mic to the left channel and the treble strings' mic to the right channel.Run a test performance by playing the piano and adjust both mics as necessary.
In noisy stage situations, adjust the mics to about six inches away from the strings, instead of 12 inches away. This will help to minimize the stage noise and bleed problems from other instruments. Also, feedback can occur when mic placement is in a given spot or the record level is too high. Do test recordings until the noise settles down. Make sure you have people walk by the piano to change the acoustic field so you can see if feedback could occur.
An instrument mic with a switchable bass cut/rolloff filter is recommended for most piano miking situations. If you find that the volume with these two mics is too low, then add a dynamic mic near the treble strings.
Miking the Upright Piano:
Grab a mic stand equipped with a boom and place the mic about six inches from the back of the piano a right around middle C. Do a test performance by playing the piano. Move the mic a foot to the left, play and listen, then move the mic one foot to the right of middle C and play and listen. Pick the best position with the best sound and then fine tune as necessary.
You may want to add a second mic if you cannot get the full range of sound. Every stage setup is different.Once again, a mic with a switchable bass cut/rolloff filter is recommended.
Testing, adjusting and retesting is the key. Get people to listen with you from different parts of the room. If you have a half hour or so to experiment, you should achieve the sound your looking for.
Remember: Feedback will knock Jerry Seinfeld's PEZ dispenser right onto the floor and THAT could get ugly. DON'T LET IT HAPPEN TO YOU.