Singers' Formant
Studies of the frequency spectrum of trained singers, especially male singers, indicate a clear formant around 3000 Hz (between 2800 and 3400 Hz) that is absent in speech or in the spectra of untrained singers. It is thought to be associated with one or more of the higher resonances of the vocal tract. It is this increase in energy at 3000 Hz which allows singers to be heard and understood over an orchestra, which peak at much lower frequencies of around 500 Hz. This formant is actively developed through vocal training, for instance through so-called voce di strega or "witch's voice" exercises and is caused by a part of the vocal tract acting as a resonator.
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