Feodor Chaliapin as Boris Godunov, 1912. Via Wikimedia Commons (public domain).
The fact, if you think about it without habit, is physically absurd: one person alone, with no amplification whatsoever, is clearly audible above an orchestra of eighty instruments, in a hall of two thousand seats, all the way to the last row of the gallery. It happens every night in every opera house in the world, and it is the only modern mass spectacle that refuses the microphone by statute. The trick exists, and it is one of the most elegant in acoustics.
It is called the singer’s formant, and science has been measuring it for decades: trained opera singers concentrate an enormous share of the voice’s energy in a band of frequencies around three thousand hertz. The choice is not aesthetic, it is strategic: the orchestra has little to say in that zone, because the mass of its sound lives lower down; and the human ear, by design, is most sensitive precisely around those frequencies. The singer, in practice, is not shouting louder than the orchestra, but speaking on a channel the orchestra leaves free and that the audience’s brain listens to preferentially. That is the squillo, the metallic blade you hear in important voices even when they sing softly, and it is manufactured with years of work on the resonator everyone carries in the throat: lowering the larynx, widening the right tube, tuning the body the way a hall is tuned.
The whole technique of operatic singing descends from this physics, and so does the repertoire: nineteenth-century orchestrations are written knowing where the voice passes, with the sopranos’ high notes placed where the body resonates best and the instrumental doublings stepping aside at the right moment. Even Tosi’s old rules on the steady, supported voice are, read today, instructions for maximising the formant. And here lies the difference in kind from amplified singing: the microphone, from the 1920s on, allowed intimacy, the whisper, crooning, that is, a new and legitimate expressiveness; but it moved the work from the body to the sound system. The opera singer remains the last athlete of the naked voice: the instrument is entirely biological, has no knobs, and when the hall is big the only recourse available is technique.
For the audience, the advice is experimental: at the next opera, in a tutti moment, chorus and orchestra at forte with a soloist on top, close your eyes and notice how the voice is not louder than the rest, and yet stands in front, as if written in a different ink. That is the three thousand hertz at work. And it is also the answer to the question that resurfaces every so often, whether it might not be better to amplify opera: it can be done, it is done in large open-air spaces, but every decibel added by the sound system takes meaning away from a technical heritage built over three centuries so as not to need one. The day the opera house switched on the microphones out of laziness, we would not have gained volume: we would have lost the last entirely human sound left on the market.