Grand & Band
Recording engineers also know there are many ways to mic a piano, as long as it’s in an isolation booth or room.
All of these open-lid techniques provide little isolation from adjacent instruments, floor monitors or the main PA when used in rhythm sections with sound reinforcement.
A grand piano’s open lid not only reflects sound outwards, but also directs outside sound back in. Even with its lid opening away from a nearby drum kit, drums can be heard almost as loud as the piano in the mics, blurred by the transfer of sound through the piano’s resonant wooden structure and the reflections within.
Closing the lid requires mics to be placed much closer than would be optimal. Since much of the sound now arrives from off-axis, mics with an even polar response perform better. A few inches over the strings, the sound pressure inside a concert grand can be 130 dB, requiring high-headroom mics.
Heavy-handed EQ is often needed to remove boxy-sounding low-mids with the lid shut completely. Because a piano is a highly resonant acoustic instrument, channel EQ must be carefully cut in specific regions between 100 Hz and 1 kHz, sometimes requiring all four parametric filters on an input channel in addition to its high-pass filter.
An old-school live sound trick, especially in a rhythm-section context, is simply using a dynamic mic aimed at the sound board through a hole in the piano’s metal frame on its curved edge, providing warmth and isolation with the lid closed. Road-dogs would lay an SM58 on a piece of foam, or wrap it in a sheet of foam, to make a short tunnel around its end that can squeeze into a piano’s sound hole, looking into the hole at an angle so it fits below the closed lid.
A sound-hole mic can be combined with any of the condenser pair techniques, or just used alone for monitors. If the wedges are tuned for vocal mics, using another makes it easier to put it in the wedges without feeding back.
Closing the piano lid reduces the clearance above the strings to about six inches, favoring side-address condensers, another reason C414s are so common for grand pianos. Other popular side-address condensers include Audix SCX-25A, Audio-Technica AT4050 and the new AT5045, Shure KSM 32 and the new BETA 181, and Sennheiser MK4 and the new MK8.
The piano harp’s cast iron frame holds 20 tons of string tension. The location and arrangement of its struts provide consistent locations for installing “gaffers-tape bridges” – an age-old method for mounting mics in a closed piano. They’re installed by simply overlapping two pieces of tape across a pair of the piano harp’s struts, making a horizontal sling for the mic, with another strip of tape on top to secure it.
The center of the piano, where the low and low-mid strings cross over each other, is well served by two struts that are easily bridged. The high end of the piano has a strut between the high and high-mid strings that dictates the gaffers-tape bridge placement of the high mic.
Since the highest strings sound metallic when miked too closely and aren’t played as much as the high-mid strings whose keys fall under the pianist’s right hand, the bridge for the piano’s high mic naturally goes across the high- to low-mid struts and provides attack from its proximity to the felt hammers.
End-address SDCs can also be used on gaffers-tape bridges as spaced pairs, though often placed more toward the middle while aimed toward the action. It’s imperative to use high-quality tape, deploying two strips underneath the mic – especially with LDCs – and if the gig is at the same venue for more than a day, to go back and check, if not re-tape it daily.
As the tape dries out, which is common in air-conditioned halls, it can stretch or lose its grip. Anyone who’s had a mic land on piano strings while it’s being played will never forget the experience.