In 1966, The Mamas & The Papas scored a No. 1 hit with the bittersweet “Monday, Monday.” The song, written by John Phillips, contrasts the band’s trademark sunny harmonies with lyrics about the letdown after the weekend’s joy. Its polished folk-pop sound (highlighted by Cass Elliot’s rich vocals) earned it a Grammy Award and secured its place as one of the defining hits of the ’60s folk rock era.