Miking The Grand Piano

By Nathan Rosenberg

I started recording pianos before recording anything else, probably because I am a pianist. It is a notoriously difficult instrument to record, so when the editors of Recording asked me to write about miking acoustic pianos, I began by asking myself What if I had known then what I know now?”

What's the trouble?

The piano is a complicated contraption consisting of up to 7000 discrete parts. Hundreds of strings resonate sympathetically and then project in unpredictable directions. Challenges include reflections within the case, tuning, leakage from other instruments, and the sheer fact that no two pianos sound exactly alike. Then there's the wide range of pitches, from the lowest A (beneath the lowest E on a bass) to the highest C (which is also the highest note on the piccolo)—your mics have to be able to capture the full spectrum.

Finally, the sheer size of the Grand with its expanse of strings and the two-position lid calls for placement experimentation—too close and you might not capture the full range and miss out on the room sound, too far and you may get less definition and more room than is desirable.

Tone, tuning, placement

Every instrument has registers and dynamics where it sounds the best. Listen, enlist the help of the player or arranger, and get the best result from the instrument and the part. It pays to be flexible.

Piano tuning is an art, not a science. No two tunings sound exactly alike but they can all pretty noticeably change the character of an instrument. Discuss your requirements with all parties involved; a skilled piano tuner can help greatly.

Just because it's big and heavy doesn't mean you shouldn't move the Grand to the location where it sounds best in the room. Moving it gently shouldn't affect the tuning, and finding the right spot will have a profound effect on the piano's tone. Then look for the most balanced sound, in the sense that all notes from high to low have a similar sound, without any notes or note clusters sticking out more prominently than others.

Stereo—what stereo?

Piano lends itself nicely to stereo recording where two signals are split, traditionally with bass on the left and treble on the right which is the way the pianist hears it. This does not restrict you to orthodox, phase-coherent stereo techniques designed to create a strong center image. In fact, many of the techniques that follow will result in a very wide image that may not resolve perfectly to mono. Live with it.

You need to keep an eye and ear out for phase problems, whether you multi-mike and pan or record in true stereo using something like an XY technique. With all the sound bouncing around inside the case of a piano, there can be a lot of stuff out of phase. But before you use the meter, use your ears.

First, sum the mics to mono and note how the sound changes. If you lose a lot of bass or you hear some weird kind of filtering in the midrange, try switching the phase on one mic, or try moving it. A little repositioning goes a long way, and this may be enough to get things into the ballpark.

Next listen in stereo. With any luck, you will hear a bit of a phantom center image. Flip the phase again to be sure you still have it the best way. Once it sounds good in mono and stereo, you are done. But if you were to look at it with a scope, it will probably still look a mess. Give up. If it sounds fine, it probably is.

In fact, sometimes to accentuate the left-right effect, I will actually delay one channel of the stereo pair by a few hundred samples in my DAW. This purposely destroys the stereo image, making the spacing from left to right seem very wide. Think of it as the bastard child of stereo miking and tight double-tracking. It isn't necessarily a natural sound, but it can often help phase issues and sometimes makes the track hold its place better in a mix.

Leakage

With more than one player in the room, leakage is inevitable. A little bit can help keep things sounding cohesive. But drums next to the piano will bleed too much into the piano mics.

Standard procedure is to stuff mics inside the piano, shut the lid, and use as many moving blankets as you can afford. This will help some. A highpass filter on your mic or preamp can deal with some of the kick drum, but the hi-hat could be enough trouble to make you move the drum kit further away and use baffles or gobos, although they begin to defeat the benefit of recording together in the first place.

With all the sound bouncing around inside the closed box, it may sound muddy, muffled, and boxy. This makes mic choice and placement within a closed piano particularly important.

Unfortunately there is no magic formula for where to stick piano mics. The sound of a piano is too complex. I recommend making a series of test recordings with the mics in different spots to better evaluate how the sound changes from place to place. Use the positions below as a point of departure.

Mic positions—the best seat in the house

Every piano is different. Suggestions for mic positioning are just that—suggestions. Walk around the open instrument while someone is playing, cover up one ear and let the open ear guide you as to where a mic should go. Then make test recordings and evaluate them. Factor this into your time budget—if you don't, you are relying on luck.

For example, on my piano, the best seat in the house is, well, the seat. Even with the lid down, there is a beautifully balanced stereo image right where my ears are while I am playing; not too hyped, percussive or unnaturally close sounding but still not distant.

An XY pair of small-diaphragm condensers about a foot over the player's head, pointing down but not directly at the keys, reveals a great jazz tone. An omni mic a little closer, or a figure-eight, gives the added benefit of allowing you to record a piano/vocalist once you get the balance right. Be careful about player noise such as creaky benches, grunting players, and people with long clicking fingernails. And if leakage from another instrument in the room is to be an issue, then, well, as we say in NYC, fuhgetubattit!

Other sweet spots

There are often a few sweet spots to be found, despite the crazy bouncing around of sound inside the piano. For example, on a well designed Grand piano, there is often a wonderful place at the tail, just about where the back leg is, or often just outside the case. Here, the various registers tend to project in a surprisingly uniform manner. This is a great spot to place a single mic for a well-balanced mono recording.

For this technique, try a large-diaphragm condenser to capture a large full sound from the instrument. This is also a good mic choice outside the piano case because this mic position won't be adversely affected by the off-axis coloration that is often present in many large-diaphragm mics.

A ribbon mic could work well here, too, typically capturing a good deal of room tone from its rear lobe. Another option is an XY pair of small-diaphragm condensers in this same location, although it won't give you the pronounced stereo image that you may be accustomed to; but you may get a natural, balanced and true stereo image if your piano projects here the way many do.

A happy medium is an M-S pair. In some ways this is the best of both worlds, capturing the on-axis mono signal along with the side mic which allows you to adjust the stereo width to taste. But again, if isolation from other instruments in the same room is mission-critical, this would not be my first choice because the mics are outside (or almost outside) the piano.

The missionary position

Two cardioid mics directly over the hammers, pointing down, one for the bass strings, one for the treble, is probably the most common setup that I observe, but it's not my personal favorite for most styles. It can work well for percussive styles such as rock and gospel because of the proximity to the hammers, but watch out for that hole in the middle” of the frequency range which can be a result of close-miking the top and bottom of the range.

The problem may start to go away as the lid is closed (due the many reflections inside of a piano). But these reflections can also be detrimental. A benefit of this technique, however, is that it allows the lid to be placed on the half stick” or, depending on your mic, perhaps even fully closed. With a bunch of blankets, you can get significant isolation, although you will invariably have to dial in some general tone fixes with a good eq to make up for the boxy and muffled sound of the fully enclosed piano. For this setup, check out Slider's Piano Barre (reviewed March 2000), as it can really help with positioning.

Off with your head

A variation of this position involves actually removing the lid of the piano and lifting the mics higher off the strings. This can solve some of the problems inherent with the missionary position.” Removing the lid isn't hard to do, but you will want an extra set of strong arms to make sure you don't hurt the piano or yourself. Pull out the small pins that are set into the hinges that hold the lid in place, and carefully pull the lid off, taking care not to bend the hinges.
Once this is done, you can hang the mics directly over the strings at any height. Remember that the lid is an integral part of the way a piano projects its sound, so this may or may not work for your needs. But this technique often results in a bright, nicely separated and well-balanced piano sound. Try different kinds of mics. Small-diaphragm condensers are a safe pick but if you have a good sounding room, try spaced omnis three or four feet off the strings.

Down the hatch

A lot of people like to stuff mics in and over the metal holes that cover the sound board. I suspect that there are more people that do it that way than pianos that sound good that way.

But there is an exception to every rule.

Sometimes I find this can work as a supplemental mic in setups that use more than two mics. Contrary to what you may have been told, these holes are not where the sound comes out.” But they do tend to focus certain frequencies. Sometimes it's a good place to catch an extra bit of zing,” sometimes it is just resonant and peaky. But people swear by this method so I include it, assuming there are instruments that really sound good this way.

One exception is that a dynamic mic or two (think SM58) can really capture a vintage piano-bar type sound. I suggest a fishbowl placed on top of the piano, as resonance from a glass full of dollar bills is requisite for authenticity.

Boundary mics

Another popular miking technique involves a pair of PZMs placed either along opposite side rails of the piano, pointing in toward the strings, or taped to the lid pointing down. A boundary mic is basically like one half of an omni mic, and because it sits at the far extremity of the piano, it is not subject to reflections from the rear. As is the case with a pair of spaced omnis, the stereo image really depends on how far the mics are spaced apart.

If your piano doesn't happen to sound good at its edges you are out of luck. But if it does, and you can adjust the placement to ensure good phase relationships, you might really like this sound.

Spaced pair” ORTF

Another option, and one of my favorites, is a sort of modified ORTF array. Two cardioids spaced a foot or two apart are placed at or around the unhinged side opening of a grand piano.

The mic closer to the keyboard can be thought of as a treble mic, the other as a bass. In practice, however, what you will most likely be getting is the full balanced sound from the mic near the back of the piano (remember that sweet spot I mentioned) mixed with a slightly more percussive sound from the treble” mic which is closer to the hammers.

The two mics are spaced far enough so that a rich stereo panned effect will be evident, but given their orientation, the phase issues should not be overwhelming. Another benefit of this position is that it will allow you to freely adjust the lid opening to taste: wide for a clearer sound, half stick for a lot more reflection, and there's even the possibility of blanketing the piano to reduce track bleed from other instruments. With an apparatus such as Slider's Piano Barre, you can even close the lid all the way if you have mics that can fit deeper inside. Another benefit of this technique is that, with the exception of an XY pair, it is the best way I have found to capture a true stereo” recording.

This position is a good starting point for classical recordings. With classical music, you typically don't want so much of the sound of the hammers and the inside of the case. The air around the instrument and the tone of the room is paramount. A spaced ORTF pair can be pulled away from the piano a couple of feet (or to taste) to excellent effect.

Another benefit of this setup is that you can be flexible in your choice of mics. While ORTF generally favors a small-diaphragm condenser, I find that sometimes a large-diaphragm pair can help to capture a more broad-shouldered sound. The rear of the mic will be pointing outside the piano (or in some instances the entire mic is outside), which makes the slower response and off-axis coloration, so typical of most large diaphragm condensers, less of an issue.

Many engineers favor an AKG C 12 in this application, but there is really a world of choices these days. Consider ribbons too! One of my favorites is the Beyer M160 because of its unique cardioid pickup pattern. Traditional figure-eight ribbons can also be used here (you might even substitute a Blumlein pair—see Robert Auld's review of the Royer Labs SF-24 in this issue) when the room sound is an asset; one lobe picks up the piano, the other gets the room.

Everything else

You can mix and match the abovementioned techniques to accentuate different aspects of an instrument. I have found that mixing microphone types and placements can sometimes catch elusive qualities that stereo and pseudo-stereo miking can't achieve. For example, you might want to use two different kinds of mics on the hammers. This can start to break down the stereo image, making the piano's width seem wider, like a cousin of the channel-delay technique I mentioned earlier.

Another valid technique involves using more than two mics. Perhaps the standard, over-the-hammer position works well but there might be a sound hole, where the very high frequencies seem to congregate. (My piano has one that seems to focus all the really high stuff, i.e. 10 kHz and above.) A supplemental mic here may be mixed in to capture this.

Watch out for phase problems and keep the relative distance between mics and the piano in mind when adding mics. The old three-to-one rule” states that the distance between any two mics must be at least three times the distance between the mics and the source to avoid phase problems, but it's a bit more complex than that: see John Shirley's ‘Compleat Recording Musician' on the subject in the October 2004 issue. To make your life a little easier, it might also be worthwhile to eq the stuff you don't need (in my case, everything below  6 kHz) out of the extra mic's track.

Keep in mind that reflections from the case and the lid will be intense here, so choose a mic with good off-axis response and attenuation I use an Electro-Voice RE20, which works well because of its slower response time, excellent rejection and bass response, and unpronounced proximity effect. For whatever reason, however, I have also had good luck with nearly the polar opposite: an AKG C414B-TLII (a predecessor of the C414B-XLII reviewed by Paul Stamler in this issue). Go figure.

Either way, supplement this mic with another one in the treble register, somewhere where you are going to catch that high end and punch that the other mic will miss. I would usually reach for a small-diaphragm condenser. Pan them hard left and right and see how you like it.

Don't forget to have fun

I hope this wide selection of suggestions gets you started and helps you avoid some of the cliches and pitfalls that novices can encounter when recording this big, beautiful, complex instrument. Just remember: if it sounds good, it is good.