Countless bands and musical artists have celebrated new album releases on late-night television, but no one has done so with quite the art world flair as BTS, the mega-famous K-pop boy band fronted by art enthusiast and collector RM. (The other six members are Jin, Suga, j-hope, Jimin, V, and Jung Kook.) Fresh off a four-year hiatus, BTS’s new album *Arirang* came out on ## Mar. 20 . The band was interviewed on *The Tonight Show Starring Jimmy Fallon* on Wednesday night. But instead of performing their new single “SWIM” in Studio 6B, Fallon played a previously recorded video from a secret live performance at the Guggenheim Museum earlier that day. In the video, Fallon stands in front of a circular stage on the ground floor of “New York’s iconic Guggenheim Museum,” as the host puts it, and introduces the song. All seven BTS members take turns singing while strolling separately down the museum ramp, with Carol Bove’s colorful metal sculptures acting as a backdrop to the performance.…