Jack Black’s character in the movie “High Fidelity” famously complained that he didn’t want to listen to Belle & Sebastian because it was “sad-bastard music.” After four proper studio albums, apparently Belle & Sebastian has had its fill of the sad-bastard thing, too. Or at least by its standard it has. On the latest B&S outing, the Scottish collective—the beloved poster children of mid-’90s indie rock cool—lightens up with the help of . . . that’s right, T.a.t.u. and Frankie Goes to Hollywood producer Trevor Horn. On paper, his pairing with a band that specializes in literate and precocious chamber pop seems downright bizarre. However, it works swimmingly. On “Dear Catastrophe Waitress,” the band filters everything from new wave (“Stay Loose”) to ’70s soul (“If She Wants Me”) through its unique perspective to deliver its best album in years.—BG