David C. Taylor, The Psychology of Singing
“ Every blemish on the beauty of a vocal tone, every fine shade of quality which detracts from its perfection, indicates to the critical hearer some faulty action of the singer's vocal organs. The more faulty the musical character of the singer's tones the more pronounced is this impression of faulty production. On the other hand, just so nearly as the singer's tones approach perfection as musical sounds, so do they also impress the ear of the critical listener as indicating the approach to the perfect vocal action. ”
