Miking a piano on stage is a deceptively simple task. Open the lid, throw a couple of mics inside, and off you go, right? Um, no. Unfortunately, there’s more to it than that. An acoustic piano is a complex instrument capable of a wide range of dynamics and frequencies, arguably making it the most difficult instrument to capture on stage (or in the studio). There’s a million different ways to do it, but here are some proven techniques to get you started.
An important characteristic of the piano is that the high strings are on the player’s right, and the low strings are on the player’s left. Separate mics are usually used for each of those sections. The issue of whether to pan the mics hard (or not) in a stereo mix is an issue with which Mozart himself undoubtedly struggled. Some people feel it’s unrealistic to have the low strings coming from one side of the house mix and the high strings coming from the other side. Use your judgment.
Don’t Flip Your Lid
Let’s assume that you are dealing with some sort of acoustic baby grand or grand piano (we’ll discuss uprights momentarily). First thing is to get the lid open. You are never going to place mics on the outside of a piano with the lid closed. Next, stick your head in there and listen while someone plays. Move your head around and try to find a “sweet spot.” La Cerra’s corollary to Murphy’s Law states, “The sweet spot will be in the location most difficult to access with microphones.” Having said that, there’s still a lot of leeway for adjustment.
If you look inside the lid, you’ll notice that the piano’s action moves the hammers up toward the strings. That’s where the attack is strongest, and that’s what helps the instrument cut through a busy mix, though it may not be appropriate for classical music. The keyboard of an 88-key piano is just about four feet long. Start with a mic approximately one foot from each end of the keyboard, four or five inches above the strings, about a foot from the hammers. The mics can face straight down toward the soundboard, or you can angle them slightly toward the low strings. Some engineers angle them as much as 45 degrees. If you need more attack, move the mics closer to the hammers.
What microphones should you use? Ideally, a pair of large-diaphragm cardioid condenser mics, but that may make it difficult to close the lid. Some engineers use a pair of small-diaphragm, cardioid condenser microphones, and here’s where we get into sticky territory. End-address mics, such as Shure SM81s or Neumann KM184s, will require the lid to be lifted at least to half-stick (possibly to full-stick). Lifting the lid invites leakage from the stage and increases the possibility of feedback from stage wedges. Closing the lid reduces leakage and feedback, but makes it difficult to place the microphones and (depending on the mic pickup pattern) may be detrimental to the sound. This is where a side-address mic, such as the Audio-Technica AT5045, Audix SCX25a or AKG C414, is your friend. As you can place the body of such mics parallel to the strings, you’ll be able to get the lid closed to half-stick far more easily. In fact, you may be able to close the lid all the way (though you may need to coax the player into this idea). A few felt bumpers on the rim of the piano case allow room for the mic cables to safely exit the piano.
When there are no other instruments onstage, you can open the lid to full stick and use one of my favorite techniques: a pair of small-diaphragm cardioid condensers in X-Y stereo. Place them eight to ten inches above the strings, pulled back slightly from the hammers. Don’t center the pair toward the middle of the keyboard — move them about two-thirds of the way toward the high keys. You’ll get plenty of low end, because the low frequencies are less directional. X-Y stereo is mono-compatible in case Grandma is still watching on a black and white TV.
As with miking toms, the detail and extended high-frequency response captured by condenser mics can also increase leakage, so in a high-volume rock situation, you might be better off with a pair of Shure SM57s or Granelli Audio Labs’ G5790 (modified 57), which has the capsule at 90 degrees to the mic body. A third mic, placed at the rounded end of the piano, a few inches above the soundboard or peeking through one of the holes in the metal frame can add low end if the first two mics need help. Be sure to check the phase of this mic relative to the other two so you don’t cause any phase issues. In fact, make sure you check phase between the first two mics as well.
The difficulty of placing microphones inside a piano is not lost upon microphone manufacturers. Many have developed kits that include mics and mounting solutions to facilitate placement inside a piano. Audix has the SCX-25a PS, which includes a pair of SCX-25a mics and holders that can be clamped to the piano frame. Earthworks’ PM40T Touring PianoMic™ system features a clever telescopic mounting bar and a pair of omni condensers. The omni pattern enables the mics to be placed close to the soundboard without suffering proximity effect. DPA’s d:vote 4099P system includes two supercardioid condenser mics and a magnetic mounting system to stabilize mic position without clamps. All of these products provide the distinct advantage of allowing you to close the lid.
No Pressure In This Zone
Another technique employs one or two boundary microphones or Crown PZM microphones. A boundary microphone usually has a very small diaphragm and is designed to be mounted upon a surface such as a floor or table. Boundary mics do not suffer the comb filtering that happens to a “normal” mic because direct and reflected sounds reach the diaphragm of a boundary mic nearly at the same time. The result is a very natural, clear sound that is consistent from all directions. The trick here is taping the boundary mic(s) to the lid of the piano, and then closing it. You can try this with the lid open, but experience has shown that it works better with the lid closed. Success with this technique varies. I’ve had amazing results on some pianos, and ho-hum results on others — all with the same pair of modified old-school Radio Shack PZMs — you know, the one in the red box that you see at flea markets? Grab it next time and search the web for DIY mods which can turn those things into eminently useful audio tools. Once again, closing the lid helps control leakage and feedback, and (bonus) you won’t have to fiddle with mic stands. Please use tape that will not remove the finish from the inside of the piano lid.
Stand Up Straight
An upright piano permits limited access to the interior, which translates to less flexibility in microphone placement. Typically, you can lift the lid to gain access to the strings, but it’s doubtful that you’ll be able to start removing panels from the case as studio engineers often do when recording an upright. Once you’ve got that lid open, use your ears to find a sweet spot as a starting point for mic placement. If you can get the mics inside the case, bleed will be reduced, and it’s fairly easy to drape a moving blanket over the top to improve isolation. As you move a directional mic closer to the interior of the case, that mic will emphasize a particular register and probably produce proximity effect. Wide cardioid (or possibly even omni) mics placed inside the case can balance the voicing even when you get close, while still rejecting some of the unwanted stage sound.
Depending upon the instrument, you may get a good result by placing mics at the back of an upright, aimed at the soundboard. The trick here is keeping the instrument away from a wall, because reflections that come back to the mic can cause comb filtering. You might be able to make this work in a house of worship situation, but it’s unlikely to be friendly on stage.
Keep in mind that the high-pass filter on the input channel is your friend. It will enable you to control proximity effect and cut pedal noise as well as other unwanted rumbly sounds that often reach a mic through the stand. You may find that once the piano is in the mix with bass and other instruments, you can actually set the HPF fairly high without a noticeable loss of low-end. It should go without saying, but we’ll say it anyway: do your best to aim wedge monitors so that they don’t blow directly toward the mics.
Steve “Woody” La Cerra is the tour manager and Front of House engineer for Blue Öyster Cult.
