The choir finished out last note, holding it and fading away. But a different note continued, floating above us, at a perfect fifth above the altos. Large grins bloomed on the faces of those of us who realized what we’d done. We’d been so in tune, and so intense, that we’d raised a harmonic from the chancel that echoed back into the nave (where we were sitting). There’s a reason I prefer singing from the nave than from the chancel in this particular space!
A description of the setting is, perhaps, in order. We were singing in a stone, wood, and glass church. It is relatively new, rebuilt after a fire in a different building spread to the chapel. The shape is cruciform, with a relatively narrow nave, short and fat transept, and a very high and relatively open central area. The support beams are very heavy wood, bolted together, and somewhat open. The time was about eight thirty PM, and the weather was a steady rain that muffled some of the street noises from outside. The space tends to echo, although not for as long as you’d think – only two or three seconds. In comparison, the church where I sing most of the time, when we take out the pew pads, has a two second echo, and it is all wood and plaster, auditorium style. (With the pew pads it’s almost dead, unless you know just where to stand, and your voice happens to hit the room’s sweet spot. You can guess how I discovered this.)
Harmonics are not always desirable, in the sense that there are times when you don’t want to add notes to whatever you are working on. The technical term is a harmonic overtone, and you can get them at least two ways. One is what happens, usually in styles like Barbershop Quartet singing, where the vocal parts interact so that the waves from the upper part of the four notes are heard as a fifth note. Another way is when the choir, or soloist, finds a note or combination of notes that resonates with the structure around them, creating an overtone. This is usually either an octave or a fifth, at least based on my personal encounters with them. I grew up hearing it called “a harmonic,” although the proper term is overtone. It does not happen often, because everything has to be exactly right, clear, precise, and the sound waves from the different parts must interact in just the proper way. I only hear it with acapella music, but that might be because I sing so much acapella music.
The human voice does not produce a truly pure tone, not even boy sopranos and altos. What we do is produce a fundamental tone with partial tones around it. The fundamental is the “note” you want to sing (or play, for instruments) and the partials are sort of a fuzz above and below. Sort of like vibrato, but on a much less obvious scale (pun intended). How those partials interact leads in part to audible overtones.
This is not “overtone singing” like throat singing. It isn’t something the singer does physically, but how the acoustics interlock and respond.
For those who are curious, we got one on “O Vos Omnes” (Pablo Casals) and one on “Ave Maria” (Franz Biebl).