Belle and Sebastian made their fragile bones whispering indie-pop songs about bicurious bookworms with huge cardigan collections. Lately, the Scottish septet have pursued more universal pleasures. “Make me dance,” frontman Stuart Murdoch entreats over a soul groove on B&S’ eighth disc, which loads up on Sixties-pop goodies without diluting the group’s willowy kink. Murdoch duets with Norah Jones on the slow jam “Little Lou, Ugly Jack, Prophet John,” and Brit actress Carey Mulligan sings the part of a crushed-out office girl on the Swinging London title track. It’s the sound of wallflowers owning the party.