The piano produces one of the widest ranges of tones and dynamics of any acoustical instrument. These characteristics make the piano an instrument of choice for worship and praise. However, these same characteristics also make the piano one of the most difficult to record or reinforce with microphones.
Is a microphone needed?
Your first question should really be, "Does the piano need to be amplified through the sound system?"
Unless there are other instruments, vocals or sound tracks that may drown out the piano, it is better to rely on natural sound instead of amplification. By repositioning the piano and increasing the opening of the lid it may be possible to eliminate the need for amplification.
If you have determined that amplification is actually needed, the next step is to choose the best microphone.
What type of microphone is best for piano?
When looking for a microphone for a piano, look for a microphone designed for instruments versus one designed for voice (Figure 1). Microphones designed for vocal use often have their bass or low frequency response rolled off to compensate for the bass boost when a directional microphone is held close to a vocalist's mouth. Vocal microphones also tend to have a slight boost in their upper mid range frequency response. This "presence peak" helps to increase intelligibility and "bring out" the vocals. While the vocal microphone characteristics enhance the voice, they diminish the sound of the piano.
Figure 1
Above: Vocal and Instrument microphones.
Below: A Frequency Response curve for Vocal and Instrument Microphones.
Microphones designed for instruments have a flat frequency response. This flat response reproduces the piano naturally. In general, the best choice for a piano microphone is a good quality condenser instrument microphone with a very broad frequency response to faithfully reproduce all of the low and high end frequencies a piano produces.
How many microphones work best for a piano?
After selecting a microphone, it's time to consider how many are needed. Always remember the "Golden Rule" of microphone technique, "The fewer number of microphones, the better." In other words, if one microphone will do an adequate job, two microphones do not necessarily improve the sound.
How should the lid be positioned for best results?
At full-stick?
If the piano lid is at "full stick" one microphone is often placed in the curve of the piano. Point the microphone toward the inside face of the lid. This usually produces a very full, uniform sound (Figure 2).
Figure 2
Place the microphone in the curve of the piano.
If sound from other instruments or vocals are "bleeding" into the piano microphone, then use the directional characteristics of a cardioid microphone and point it so the rear of the microphone is aiming toward the worst offenders. You may also find it useful to bring the microphone closer to the piano. Aim the microphone toward the area where the hammers strike the strings.
Closed lid?
If the piano lid is completely closed, placing microphones inside the piano is a poor solution. A boundary microphone will work, but certainly not very well. A better approach is to mount a microphone on a boom stand and place the microphone over the bass string hammers and point it across the hammers to the treble string hammers. (Figure 3).
Figure 3
Position the microphone over the bass hammer and
point it across the treble string hammers.
What happens when the piano lid position must change from one type of service or program to another? A good solution is to use a special type of transducer called a C-ducer. This is a special type of piezo-electric ribbon mounted directly to the sounding board of the piano. The C-ducer provides the best isolation from other instruments, and it produces a consistent sound regardless of the position of the lid. The C-ducer is available in mono or stereo versions. Another similar piano "pickup" is made by Helpenstill. Both of these types of transducers will produce a very "dry" or "sterile" sound. If these microphones are used for recording, a digital reverb should be used.
Another approach that works very well for both closed and open piano lids uses two identical unidirectional instrument microphones. Mount them on two boom microphone stands. Locate them over the hammers, centered over the keyboard. Try to position them so the two microphone elements (front) are as close to each other as possible. Aim the "left" microphone toward the treble hammers on the "right," and aim the "right" microphone toward the bass hammers on the "left." This approach also works well for stereo piano recording, while maintaining compatibility with the monaural sound reinforcement system. (Figure 4)
Figure 4
Aim the "left" microphone toward the treble hammers and
the "right" microphone toward the bass hammers.
What are some general rules of the piano?
Keep in mind the acoustics of a piano. As you place the microphone(s) further inside the piano, the sound of the piano will become less natural. The piano was designed so the sound would fully develop at a distance by using the reflective property of the piano lid.
If you must place the microphones further inside the piano, make certain that you place them closer to the hammer/string area, but not pointed straight down toward the sounding board. Angle them toward the row of hammers. The closer you place the microphones to the hammer/string area, the brighter and more distinct the resultant sound will be. Putting them too close will emphasize certain individual strings and these notes will become overly prominent.
One special type of microphone that works well on pianos is the "boundary" or "plate" microphone. When mounted to a fairly large surface, a piano lid for example, boundary microphones have a hemispherical pattern. This approach can offer a substantial improvement over the hollow sound that is usually heard when a conventional microphone is placed too far inside the piano. However, boundary microphones are not perfect either. Due to its hemispherical pattern, if the piano is used at "full stick," the boundary microphone will be more sensitive to sound from nearby instruments or voices or "bleed."
Newer boundary microphones have been designed with a unidirectional pattern. The best location for this specific type of boundary microphone is the inside of the piano lid, at the edge of the piano lid (closed or short stick) closest to the hammers. Place the microphone in the center of the keyboard. Aim the "front" of the microphone toward the hammers and the "back" of the microphone toward the body of the piano. (Figure 5)
Figure 5
Mount the microphone to the underside of the lid.
Point the "front" of the microphone toward hammers.
Experiment.
If you have several different microphones and aren't sure which one(s) to use on the piano, then experiment. Try placing two microphones next to each other and listen while switching back and forth between the two. It works great to use headphones. If you aren't sure where to place the microphones, place identical microphones at several spots and perform the same comparison test as mentioned above. Don't be afraid to experiment.
by Travis Ludwig © 1996 Internet Sound Institute (www.soundinstitute.com). This article is for personal use only. Any commercial reproduction is not permitted without permission. To obtain permission, contact ISI at hopi@soundinstitute.com
