If you listen closely you can hear Alagna going sharp by nearly half a step.

And for those of you paying attention, Palombi was NOT the lead cover, he was the third in line. On hearing Alagna wack his piece, Palombi figured on Alagna walking off and dashed to the stage to take his place. Poor form to take another chap's place in line, but fortune favors the bold, I suppose.

Oh, and the term that is generally used in opera is cover, not understudy. (Understudies are for theatrical plays.)

http://operachic.typepad.com/opera_chic/2006/12/palombi_we_saw_.html

*edited for clarity*

Dag is it also possible to add a small HTML section in the FAQ as well for people who have problems in how to make basic HTML editing changes and links?