Silvery voice of a great Jussi Björling is still unsurpassed: Jussi Björling’s flawless vocal technique, silvery beauty of tone, gleaming upper register, and superb interpretive skills have made him one of the greatest and most beloved tenors of the twentieth century. Numerous colleagues as well as music critics have long placed him at the very pinnacle of vocal excellence. It was to Jussi that Dorothy Caruso, widow of Enrico Caruso, said, "You are the only one worthy to wear his mantle, bear Rico’s crown!"
Thinking of Björling's chiaroscuro - transitory changes in vowel sound or registration balance can be made quite healthily for affect, providing that the singer never loses sight of his true timbre & vocal balance, & returns to them.