I haven't had to mic up a live piano in a while but I wound up talking to someone about it the other day. The simple answer is that there is really no wrong way to do it. You use what you have available and try different things to get the sound you want out of it. You don't have to invest $8000 on some custom tailored piano bar mic. Anything from the humble SM57 on up will get sound into the PA or on to tape. (I use the tape as a nickname for any type of recording, old habits die hard.)
What really matters most is the positioning and how the piano itself sounds and is set up. On an upright you can mic the sound board or the more adventurous might try opening the lid and delving inside. On stage a solo piano will be wide open and facing the audience. Sharing the stage with a rock band means the lid will be closed (maybe at half stick in some cases). That can restrict what you're doing but a PZM and some gaff tape can be used to get decent sounds from inside a closed piano. Sometimes it's more about keeping the band out of the piano than anything else.
Let's go with a grand piano with the lid open. Probably most people won't have access to a Steinway or a Bosendorfer so let's assume it's something commonly seen like a Yamaha baby grand. These examples are all for a single mic and a mono recording. We'll save the live stuff for another time. First you have to choose what type of sound you're looking for. Dynamic mics will sound less detailed but shouldn't be ruled out.As you get into more complex mic arrangements having a less sensitive mic as part of it can be useful for getting more body into the sound.
For something ambient a good choice can be to place the mic near the player's head. It's a common place to hear a piano from and should sound pretty familiar. The next most logical spot would be looking into the guts of the piano from a few feet away. But don't stop there. Try it from farther away, mic the wall, tuck the mic up by the ceiling, go nuts.
Another approach is to go for close micing. This is a great way to go if you'll be adding reverb later. One quick and dirty solution is to just stuff that old SM57 in close to the sound board, somewhere around the fourth or fifth hole. For more attack you can move closer to the hammers. For more highs or lows you can move back and forth. Again, don't stop there. I heard a story once about micing the under side of the open lid with a 421 from about an inch away. I've tried it a couple times and when you find just the right spot it can be amazing.
Something that gets forgotten a lot is underneath the piano. Whether your top and/or ambient mics are mono or stereo, having a mic under the case can be a great tool to add some serious low end resonance. It's sort of like micing the back of a guitar amp. Not a choice you'd ever go with on its own, but killer in the right combination.
Take a listen Brethren of the Knob and fader. I spent a few minutes with our little old Yamaha at work and got a few captures for you. The sky is the limit if you're willing to spend a little time experimenting.
- Mini Podcast - Piano Micing - Three mics in different positions around a baby grand.