Nathaniel Rateliff & The Night Sweats are having a moment. After the soul sensations’ Aug. 5 performance on The Tonight Show Starring Jimmy Fallon went viral, the band’s foot-stomping drinking song “S.O.B.” ignited at radio, becoming the No. 1 add to alternative and the No. 1 viral track slot globally on Spotify. Questlove praised the act’s TV debut on Twitter, as did Stephen King. And then, Sir Paul called to rave. “That guy the other night -- son of a bitch,” Fallon recalled to Billboard, doing his best McCartney impression. “They set the place on fire.”

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After seeing a YouTube clip of the Denver group, the late-night host forwarded it to music booker Julie Gurovitsch, insisting she lock the band in “the sooner, the better.” As Gurovitsch tells Billboard, “Once Jimmy saw the video, he was such a fan, it was electric.” During the taping, Fallon even played a clip of the song during his opening monologue -- a genuine enthusiasm reserved for his personal favorites. “I swear he would be so good in A&R,” adds Gurovitsch. “Man, oh man, [they] hit a homer,” says Fallon. “Standing ovation.”

The appearance helped the band sell 20,000 copies of its eponymous album in its first week, and has since forced the group to alter the scope of its current tour. “We just upgraded rooms in New Orleans and Dallas,” notes manager Chris Tetzeli.

As for Rateliff, the Missouri-born artist is just happy people are finally listening. “I don’t really get jitters, but we had a couple of drinks,” admits the 36-year-old about the preshow preparation. “It’s hard to anticipate that sort of reaction. Jimmy jumped up onstage, and then we all had a little toast afterward.”

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While the attention has catapulted Rateliff to a new level, the plan is still to work his new record for the next 18 months. “He’s relatable to the average American,” says Fantasy Label Group president Margi Cheske, who was instrumental in placing Rateliff on the legendary Stax imprint (Otis Redding, Mavis Staples). “He is the real deal.”

This article originally appeared in the Sept. 26 issue of Billboard.