Griffith: "Vocal Mastery is acquired through correct understanding of what constitutes pure vowel sounds, and such control of the breath as will enable one to convert every atom of breath into singing tone. This establishes correct action of the vocal chords and puts the singer in possession of the various tints of the voice.
"When the vocal chords are allowed to produce pure vowels, correct action is the result, and with proper breath support, Vocal Mastery can be assured."
Duval: "What is Vocal Mastery? Every great artist has his own peculiar manner of accomplishing results—has his own vocal mastery. Patti had one kind, Maurel another, Lehmann still another. Caruso may also be said to have his own vocal mastery.
"In fine, as every great artist is different from his compeers, there can be no fixed and fast standard of vocal mastery, except the mastery of doing a great thing greatly and convincingly."