By Mary J. DiMeglio

MANCHESTER, Tennessee -- The always-humble Sam Smith had low expectations for his Friday afternoon (June 13) Bonnaroo Music and Arts Festival set -- so low that he bet against himself.

"I made a bet with my manager that there would be no one here, so I owe him a lot of drinks," Smith confessed early in his performance.

An enthusiastic crowd not only turned up en masse, they sang and swayed along, making the U.K. crooner and his backing band feel more than welcome.

The 22-year-old You Outta Know Artist is gearing up to release his debut album, In the Lonely Hour, on Tuesday. New songs, including "Leave Your Lover" and "Like I Can," are clearly already very familiar to his fanbase, who unabashedly belted along during his show.

"Money On My Mind" and Naughty Boy's "La La La" were crowd favorites, and time seemed to stand still during his angelic "Lay Me Down."

His album's single, "Stay With Me," which is blowing up the Billboard Hot 100, had the audience absolutely swooning.

To fill out his hour-long set, Smith presented his terrific cover of the Arctic Monkeys' perfect "Do I Wanna Know?"

Smith hinted that he will take the same stage later Friday night with U.K. producers Disclosure. It's a safe bet: Their "Latch" collaboration is what made him a star -- even if he's still not ready to believe it.