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 know (and her few existing film clips confirm) that her power flowed not from excess but from unbroken concentration, unfaltering truth in the moment. It flowed also from irreproachable musicianship. People say that Callas would not hesitate to distort a vocal line for dramatic effect. In the throes of operatic passion plenty of singers snarl, growl, whine, and shriek. Callas was not one of them. She found all she needed in the notes.