After a six-year break during which frontman Robin Pecknold vanished to the Washington woods then reappeared as a college student in New York, Fleet Foxes return with a fresh sense of purpose. Expanding on the harmony-driven sound of their first two albums, Crack-Up boasts both pretty, straightforward folk tunes (“Naiads, Cassadies,” “Fool’s Errand”) and sprawling, suite-like explorations (“Third of May / Odaigahara,” “I Am All That I Need / Arroyo Seco / Thumbprint Scar”) that are at once comforting and quietly avant-garde. It’s a balance that allows the band’s natural sweetness—and wild ambition—to shine.