Madonna was the surprise guest at Monday night's Carnegie Hall

benefit for the Rainforest Foundation, which was hosted by foundation co-

founder Sting and also featured Elton John, Billy Joel,

Roberta Flack and James Taylor singing a number of Beatles

classics during the second half of the performance. The former Material Girl

performed her latest single, "Frozen," and also joined the entire lineup onstage

for a closing romp through "With A Little Help From My Friends" and "Twist And

Shout." The ninth annual concert raised an estimated $2 million, according to

Rainforest Foundation spokeswoman Myra Scheer.