Maria Callas (December 2, 1923 – September 16, 1977) was an American-born Greek soprano who was one of the most renowned and influential opera singers of the 20th century. Many critics praised her bel canto technique, wide-ranging voice and drama...

In 1968, Callas told Lord Harewood:

"De Hildalgo had the real great training, maybe even the last real training of the real bel canto . As a young girl—thirteen years old—I was immediately thrown into her arms, meaning that I learned the secrets, the ways of this bel canto...

Matthew Gurewitsch: "In fact the essence of her art was refinement. The term seems odd for a performer whose imagination and means of expression were so prodigious. She was eminently capable of the grand gesture; still, judging strictly from the evidence of her recordings, we kno...

"The tone of the voice was warm, lyrical, intense; it swirled and flared like a flame and filled the air with melodious reverberations like a carillon. It was by any standards an amazing phenomenon, or rather it was a great talent that needed control, technical training and strict discipline in o...