Recording an acoustic piano presents enormous challenges for many home recordists. The instrument's size and sonic complexity are contributing factors, making great technical demands on mics and other recording equipment, but that's only part of the problem. For a start, few of us are lucky enough to have access to a decent piano for a long enough period to develop any significant experience of recording it. There's also the fact that the number of 'correct' mic techniques is enormous, yet any given one of these might be completely inappropriate for the sound you're after.

The aim of this article is to take some of the guesswork out of getting a great piano sound, bringing together a wide range of recording techniques suggested by various different authorities and then illustrating them with audio examples. Surf to , and judge for yourself whether these techniques are the dog's danglies or a dog's dinner.

Because of the nature of the piano as an instrument, certain types of microphone lend themselves better to recording it than others. It should be pretty obvious that the piano generates a very wide frequency range, starting at around 26Hz (the fundamental frequency of the lowest note) and extending well beyond the 20kHz upper limit of the audible spectrum. This makes most dynamic mics a questionable choice, as their comparatively heavy diaphragms simply can't track the delicate, fast air movements of the highest frequencies as well as can lighter ribbon- or condenser-mic diaphragms. For the same reason, dynamic mics tend to blunt the edges of the piano's percussive transients, so unless you're after a special effect, leave your SM57s in the cupboard (that said, engineer Geoff Emerick has said that his favourite piano-miking technique for Beatles sessions comprised a pair of AKG D19 dynamics — there's always one...)

The extended range of the piano's low frequencies is also relevant to the choice of polar pattern. The frequency-response charts of many directional mics tend to dive much more rapidly at the low end than those of omnidirectional designs, and this is one reason why omnis are often chosen. Directional mics also exhibit proximity effect, and this bass boost can make it difficult to get an even sound when close-miking the inside of the piano.

The sheer dimensions of the instrument are another reason why many engineers choose omni mics for close-miking. Even directional mics that have a fairly wide forward-facing lobe on their polar plot have a tendency to 'spotlight' the section of the instrument they're pointing directly at when close-miking, thus exaggerating the level of one aspect of the sound at the expense of others. A lot of engineers address this potential problem by using a coincident pair of directional mics, thereby expanding the effective pick-up width of the rig as a whole.

The off-axis response of the microphones is of particular importance with piano recording, regardless of your mic technique, because very little of the sound you're hoping to catch is likely to arrive directly on axis when you're dealing with such a large instrument. This is especially relevant to crossed-pair stereo techniques, as the sound arriving from directly in front of the setup will usually be at least 45 degrees off-axis to both mics, yet that frontal sound will typically be coming from the important mid-range strings when you're close-miking inside the piano, or from the centre of the soundstage when you're using more classical-style ambient stereo miking techniques.

Budget large-diaphragm cardioids are usually the worst offenders when it comes to this aspect of performance, particularly at high frequencies. It is easier to design small-diaphragm models with good off-axis characteristics, and omni and figure-of-eight polar patterns also tend to be better behaved in this regard as well. Another option here would be to try a boundary mic or PZM (pressure zone microphone), as these are constructed in a way which allows exceptionally even tonality across their characteristic hemispherical polar pattern. (The majority of PZMs are immune to proximity effect too, but they do need to be mounted on a large, solid, flat surface to deliver their best bass response.)

Irrespective of the model of mic used, if you're going to close-mic, check that the mic you are using can cope with high SPLs, because pianos can get very loud and create lots of powerful percussive transients which can easily distort the internal electronics of mics and preamps. Engaging the mic's pad switch is also a sensible precaution if there's one available.

With all the above factors in mind, lets look at some real examples of mics top engineers have name-checked, to see how they stack up against the theory. Perhaps surprisingly, given what I've said about off-axis response, large-diaphragm condensers are quite a common choice. Al Schmitt (the multi-Grammy-winning engineer responsible for, amongst many others, several Diana Krall records) is a great fan of the Neumann M149 for close-miking inside the piano. Jon Kelly, while discussing his work with Kate Bush in SOS June 2004, professed himself a big fan of the Neumann U87. Elliot Scheiner also mentioned using this, during the recording of Van Morrison's 'Domino' (SOS February 1996), and waxed lyrical about the AKG C12 when discussing his work on Steely Dan's album Everything Must Go in SOS August 2003. That other studio stalwart, the AKG C414, also crops up in a number of SOS interviews: Chris Kimsey used a couple for the piano on the Rolling Stones' 'Start Me Up' (SOS April 2004); Jay Graydon mentioned using a vintage C414EB for his album Bebop (SOS December 2001); and Nashville engineer Brian Tankersley opted for a spaced pair for his work on Lonestar's chart-topping track 'Amazed' (SOS October 2002).

These mics have a couple of important things in common. Firstly, they are all multi-pattern, and on the few occasions where a polar pattern is mentioned, it's usually the omni. Secondly, they are all fairly wallet-melting purchases and, as you would have every right to expect, they offer excellent low-frequency extension and about as benign an off-axis sound as you'll find from a large-diaphragm design, particularly where omni mode is used.

Small-diaphragm condensers are also common, and Ed Cherney (who's worked with high-profile piano players such as Billy Joel and Elton John) is one amongst many who single out the Brüel & Kjaer 4000-series microphones for their recordings — the mics came under the DPA (Danish Pro Audio) brand in 1992, but are still very much current products. Originally, B&K primarily manufactured measurement microphones, and they meticulously designed these small-diaphragm mics for ruler-flat frequency response both on and off axis. Ed Cherney and Jay Newland (most famously associated with the Norah Jones records) have mentioned selecting the cardioid 4011s and 4007s respectively for XY coincident miking inside the piano, while Richard King, one of Sony's senior classical recording engineers, stated a preference for a spaced pair of omnidirectional 4009s for his ambient stereo recordings. Naturally, B&K aren't the only game in town: the Neumann KM84 is another recurring favourite, numbering David Bowie's producer Tony Visconti amongst its aficionados (according to Howard Massey's book Behind The Glass), and Mike Hedges remarked in SOS July 1998 that he often goes for a pair of Sennheiser MKH40s.

Clearly, there are no easy answers when it comes to choosing a mic for recording piano, especially because certain mics are suitable only for certain techniques — so I'll be returning to this issue as we now start looking at some of the different miking approaches.

One way to record a piano is to attempt to capture its sound within a suitable room acoustic, as naturally as possible using ambient microphone techniques. These days this approach is primarily used for classical music recordings, where the intent is effectively to recreate a 'best seat in the auditorium' sound for the listener at home. This type of recording is normally too reverberant for any other music style, and because you can't really change or reduce the room sound after the recording has taken place, it limits your options during a multitrack mixdown.

The...