Page 3: The SOS Guide To Capturing A Great Acoustic Piano Sound

Moving Closer In

If you're not recording classical music, then you'd be forgiven for stifling the odd yawn so far. Why bother with all this stuff about ambient recording techniques when they are rarely appropriate for more modern commercial production styles? The answer to this question is that a lot of the same principles also apply when you're close-miking, so it's useful to have an understanding of them even when you're planning to move your mics in much closer — which is what we're going to do now.

Here you can see a number of commonly suggested close-miking setups where the mics remain outside the piano's casing. You can listen to how these sound by checking out the 'CloseOutside' audio examples.Most of the information I've found on close-miking grand pianos deals with positioning mics inside them, somewhere over the strings. However, before we get carried away with that, it's worth considering positions just outside the case, in the curve at the front of the instrument. This is an area Hugh Robjohns recommended in his piano-recording article back in SOS May 1999, and there are two different techniques like this mentioned in Huber & Runstein's Modern Recording Techniques.

Once you're this close to the instrument, the positions of the different strings inside the casing begin to have a greater impact on the sound as you move mics around. The upper strings occupy a comparatively small space behind the right-hand side of the music stand, while the mid-range and lower strings extend right down into the foot of the case, crossing over as they do so. Positioning mics closer to one set of strings or the other inevitably affects the balance of the sound, as does angling directional mics in this way.

Finding a good mic position still isn't quite as simple as that, given the reflections from the instrument's lid, so I've recorded some audio examples to give a taste of the sonic range on offer here. I set up four omni mics at different points along the curve of the piano, and also set up a coincident crossed pair in the middle. You can see how these microphones were placed relative to each other from the photos (opposite), and you can hear the resulting recordings in the following audio files:

• CloseOutsideMic1-4: The individual omni mics were all 30cm from the instrument and 30cm above the lip of the case (to minimise shadowing of the high strings). Mic one was closest to the foot of the piano and mic four was closest to the keyboard.
• CloseOutsidePair1: This stereo file combines the inner pair of omni mics to create a fairly tightly spaced stereo pair.
• CloseOutsidePair2: This stereo file combines the outer pair of omni mics for a wider image.
• CloseOutsidePair3: A crossed pair of cardioids, set up with the two capsules pointing to the high and low strings respectively.

Inside The Piano

Broadly speaking, techniques for close-miking inside the piano fall into two main categories: spaced-pair techniques and coincident techniques. Looking at the former to start with, there seem to be two main schools of thought when it comes to deciding where to put the two mics. The first is to tuck them somewhere fairly close behind the music stand, covering the two halves of the instrument's register before the low- and mid-range strings start seriously overlapping. Al Schmitt, for example, talks in Behind The Glass of setting up his pair of Neumann M149 omni mics in this way "usually a couple of feet off the high end and a couple of feet off the low end, kind of at 45 degrees to each other". He also adds, in another interview, that he tries to aim the mics at the hammers to get sufficient attack in the sound.

A variety of spaced stereo techniques can be seen in action here, as used for the 'InsideSpaced' sets of audio examples. The pair behind the music stand (in conjunction with the extra crossed pair up by the edge of the lid) was used to recreate techniques described by legendary audio engineer Al Schmitt, while the remaining four mics are set up in line with the preferences of two other experienced professional engineers, Brian Tankersley and Cookie Marenco.The second basic approach is to place one mic (typically an omni) over the middle of the group of high strings behind the music stand, and a second mic closer to the foot of the piano, catching the low- and mid-range strings roughly where they cross over. Brian Tankersley referred to this technique back in SOS October 2002, and it also crops up in Hugh Robjohns' article and Huber & Runstein's book. I came across another interesting technique courtesy of an engineer called Cookie Marenco, who uses a near-coincident rig in the middle of the piano, taking advantage of the directional characteristics of two cardioid mics to pick out the low and high strings respectively.

To compare these different sounds, I placed three pairs of Rode NT55s 30cm above the piano strings (as shown in the photo) to create the following audio files:

• InsideSpaced30cmPair1: This recording is from two omni mics behind the music stand, positioned roughly as described by Al Schmitt.
• InsideSpaced30cmPair2: Here, I had one omni mic over the high strings, and another omni closer to the foot of the piano, where the low- and mid-range strings cross over.
• InsideSpaced30cmPair3: Two cardioid mics were positioned in a near-coincident pair over the middle of the piano, with the two capsules pointing downwards and angled towards the upper and lower strings respectively.

An additional mic underneath the piano can help bolster the low end of the piano sound when close-miking — for my 'UnderPiano' audio example I used a C414B-XLS in omni mode, positioned as shown here.Irrespective of which spaced technique you might decide to use, it's worth checking how your mic setup's tonality comes across in mono. If phase cancellation is destroying your carefully adjusted sound, try shifting the mics a couple of inches in relation to each other — this will usually change the effects of the phase cancellation quite a lot in mono, while making very little difference to the sound in stereo.

You may already have spotted that there is an extra crossed pair of mics in the photo up by the crook of the lid. I put those there to check out another of Al Schmitt's recommendations, namely adding some extra stereo ambience from a crossed pair in this position to supplement the sound from the omni close mics — I used a crossed pair of Shure KSM141 cardioids for this, recording them alongside the NT55s. You can hear them on their own in the 'SchmittAmbience' audio file, and I've mixed them in with the close mics at a fairly subtle level for 'SchmittMix'. Schmitt isn't the only engineer using this kind of technique (Tony Visconti, for example, mentions using additional room mics in Behind The Glass) so it's worth having a go, especially as you can probably get away with using less high-quality mics for the ambient pair than for the main pair.

Different Heights For Close Mics

There is some disagreement amongst different authorities as to how high the mics should be within the piano, with some engineers (often in pop, blues, or rock styles) preferring a closer position, where each string is more distinct, and others (such as Al Schmitt) favouring a more distant placement where the harmonics of the different strings have more chance to blend. The more distant placement has the practical advantage that it keeps the levels of the notes in different registers sounding more even — a mic placed very close in will pick up the strings next to it much more strongly than it will the strings further away.

You can let your ears decide which sound you prefer by listening to the 'InsideSpaced15cm' audio files, which were created from the same mic positions as before, but this time with the mics only 15cm above the strings. While I was repositioning the mics, I also set up another mic (an AKG C414B-XLS omni) underneath the piano and recorded it alongside the 'InsideSpaced15cm' mics to create the 'UnderPiano' file. This mic placement was something which Paul White mentioned might be worth experimenting with in his piano-recording article back in SOS October 1994, the idea being that it picks up a more mellow sound from the soundboard.

For studio productions some engineers, notably Elton John's producer Gus Dudgeon, like to place their microphones further from the piano's strings by removing the instrument's lid. To demonstrate the effects of this approach, the 'InsideSpaced' configuration of microphones was repositioned at a greater height in this way, as you can see in the picture, and recorded to generate the 'InsideSpaced60cmLidOff' audio examples.A lot of SOS readers don't have access to omni mics, though, so what kinds of results might you be able to expect using the two spaced-omni techniques with directional mics such as cardioids instead? The biggest risk is that the directionality of the mics will 'spotlight' certain regions of the strings at the expense of others, making certain ranges of notes over-prominent, and also potentially leading to something of the hole-in-the-middle problem we've already encountered in relation to ambient miking. You'll also get a drier sound than with omnis, although you might prefer this on a subjective level. To help give an idea of the kind of change involved, listen to the 'InsideOmnisToCardioids30cm' files, where I used the same mic positions as for the first two 'InsideSpaced30cm' recordings, except that I switched the mics' omni capsules for cardioid ones.

When we interviewed Gus Dudgeon in July 2001, the legendary producer of Elton John remarked: "I never close the lid on a piano. It's the worst thing you can possibly do. Taking the lid off is even better, if you can get the lid physically off. The lid is only there to bounce the sound out into the hall when you're playing live with an orchestra." This is a view shared by a number of recording engineers, so I felt it would be worth investigating how this affects the sound by removing the lid and re-recording exactly the same mic pairs I used for the 'InsideSpaced30cm' recordings. These recordings can be heard in the 'InsideSpaced30cmLidOff' files.

Clearly, removing the lid gives you more scope to raise the mics, something which Gus Dudgeon went to great lengths to take advantage of, even though that meant building an elaborate baffle to reduce spill from other instruments during his recording sessions. To try to give a sense of what kind of difference a bit of extra height makes, I moved all my mic pairs up as far as I could (so that they were all about 60cm above the strings), and recorded the 'InsideSpaced60cmLidOff' files.

Coincident Pairs Inside The Piano

For similar reasons that some classical engineers favour coincident stereo techniques over spaced pairs, there are also devotees of coincident methods inside the piano. Probably the most commonly mentioned position is somewhere behind the music stand. Both Ed Cherney and Jay Newland advocate this approach and this option also appears in Huber & Runstein's book. Although there appears to be some consensus that a sensible height for these mics is about 20-30cm from the strings, exactly how far behind the stand the stereo pair should be seems more open to debate. Positions closer to the hammers give a brighter and more percussive sound, whereas the tone gets progressively warmer the further back you go. To hear this for yourself, check out the 'FrontToBack' audio files, where I set up six identical omni mics along the centre of the piano roughly 30cm from the strings. Mic six was right behind the music stand, and the other mics were progressively further towards the foot of the piano.

Here you can see the three coincident stereo close-miking techniques and you can compare them using the 'InsideCoincident' audio files. You can also see two extra mics at the foot of the instrument (a C414B-XLS cardioid on a stand and a Shure KSM141 omni resting on a folded towel), the placement of which follows suggestions from high-profile engineers Ed Cherney and Jay Newland.Huber & Runstein describe one other coincident position that is also worth considering. This is where the mics are placed just inside the piano (over the soundholes) at a height roughly midway between the case and the lid. The two mic capsules are then pointed diagonally down towards the low and high strings respectively to create the stereo picture. Because of the positioning over the sound holes, you get more of a contribution from the soundboard than with the other technique, which gives quite a different timbre (this is a tone for which Tony Visconti expresses a preference in Behind The Glass, although he adopts a spaced-pair approach).

The following files give some idea of how the sounds of these techniques compare in practice (you can see how all the mics were rigged from the photo, below left):

• InsideCoincidentPair1: A crossed pair of cardioids 30cm directly above the hammers, pointing downwards.
• InsideCoincidentPair2: A crossed pair of cardioids 30cm above the strings in the centre of the piano, pointing downwards.
• InsideCoincidentPair3: A crossed pair of cardioids set up just inside the front of the piano, as described in Huber & Runstein's book.

In the case of the first of these pairs of mics, the position gives quite a bright sound, so it's not uncommon for engineers to mix in the signal of a further mic to reinforced the low end. An approach that Ed Cherney has used is to mike up one of the low soundholes really close with a directional mic, such that the already bassier sound at that point of the piano is exaggerated by the proximity effect of the mic. Jay Newland also likes to put an additional mic towards the foot of the piano, resting on a piece of foam, for a similar purpose. So, while recording the above audio examples, I also had an AKG C414B-XLS cardioid mic and a Shure KSM141 omni running to test out Cherney's and Newland's techniques respectively. You can listen to these mics for yourself by downloading the 'ChernyBassMic' and 'NewlandBassMic' files.

Narrowing Down The Choices

It would be fair to say that the number of options available to the recording engineer when recording piano can be bewildering, and most home studio owners simply don't get a chance to hear enough different mic techniques to decide what does and doesn't get the sound they hear in their head. If you've been able to work your way through the audio files as you've been reading this, though, you should already have a much clearer idea of which miking approaches are likely to work best for you. That means you'll already be armed with a couple of good starting points for miking up your next piano session, and can spend the session time refining them into something that sounds stunning, rather than wasting hours eliminating masses of less suitable alternative rigs.