Kay, Elster. Bel Canto and the Sixth Sense: A discursive and technical essay on the traditional Italian physical style of singing examined by means of the facilities of modern science. London: Dobson Books, 1963. (p. 74)

‘The voice is part of the whole human structure and even the most skilfully used voice will tire. But if it is correctly used its rate of recovery is rapid and its life span very long. (The great singers of the past sang very well until they were in their seventies. The writer heard the late Mewburn Levien sing one of the Arie Antiche with strong, firm tone when he was in his ninetieth year.) On the other hand if, as many modern singers do, an attempt is made to economize the voice by constantly singing at half-cock or, to put it more precisely, with inadequate laryngeal compression and cordal tension, the voice wears badly and the span of vocal life is considerably shortened. The writer knows personally several one-time celebrated singers who have followed this course confessedly, and who are now, being in their fifties, vocally very worn and consequently passé. They were lucky to last so long.’