That quote about Christine I mentioned (which occurs right before she's taken by Erik):

"Just then, Carlotta made her entrance in a box facing the stage, a sensational entrance. Poor Christine raised her eyes upon this fresh subject of excitement. She recognized her rival. She thought she saw a sneer on her lips. That saved her. She forgot everything, in order to triumph once more.

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From that moment the prima donna sang with all her heart and soul. She tried to surpass all that she had done till then; and she succeeded. In the last act [of the Faust opera] when she began to invocation to the angels, she made all the members of the audience feel as thought they too had wings."

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*Leroux, Gaston. The Phantom of the Opera. Edited by John L. Flynn and J. R. Ward, Signet Classics, 2010, p140.