We're serving up one for the studio cats today. There are a million ways to mic up a piano, from a single mic to complicated (and expensive) setups with multiple mics. This isn't about those setups. If you're into that type of thing just get on Gearslutz or any other forum for that matter and scroll through the thousands of posts on the subject.
This trick is for when you've exhausted your mic locker and you just can't get that rich, resonant sound you want. It's dead simple too but you'll look like a rocket scientist when you pull it out so pay attention.
Just mic the underside of the piano. With anything. You'll get tons of resonance that you can blend in to taste and just get on with the session. You can mess with polarity if there's issues with your other mics. You can low pass if there's too much attack for the sound you want. That's it. The only way you can look any cooler when you pull this trick is to have a mechanic's creeper so you can roll under there like you're going to change the oil.
Well Brethren of the Knob and Fader, we're almost through with this edition of Mic Trick Week. Get your requests in quick or you'll have to wait till next time!