In Fear of the Phantom Scooby-Doo! Mystery Incorporated : Season 1 Episode 7

The Hex Girls (consists of Thorne, Dusk, and Luna), Velma's favorite band, come to Crystal Cove and plan to give the gang a concert. But things go awry when The Phantom, an evil specter, suddenly appears with the intention of permanently taking The Hex Girls out of the music business.