In reply to Eric.

Some hurt their voices by over warming up (Dame, Joan Sutherland, refused to warm up before an opera lest nothing of her voice remains for the stage). Throw in acid reflux if unclean diet, little sleep because of stage fright (Mimi's lambs' favorite excuse), plus some they-tryna-keel-me-softly-in-the-car paranoia. . .and voilà! Haha