On Saturday, Dave Grohl made an unexpected appearance at Trombone Shorty’s Voodoo Threauxdown festival in Los Angeles, where Grohl and Trombone Shorty joined forces to cover Nirvana’s “In Bloom.” As Alternative Nation points out, this is the second time Grohl has performed “In Bloom” since Nirvana broke up in 1994 following Kurt Cobain’s death. The first time was in 2014 with Nirvana’s surviving members in honor of their Rock and Roll Hall of Fame induction. Watch Grohl and Trombone Shorty’s surprise cover below.