Hopscotch Fest kicked off in Raleigh, NC on Thursday (9/5), and after Sleater-Kinney played their first show with a new drummer since Janet Weiss left the band, Lucy Dacus performed at The Pour House. As Stereogum points out, her set included a surprise guest, Tomberlin, who joined Lucy for a cover of Sufjan Steven's classic Illinois track "Casimir Pulaski Day." They had just prepared the cover earlier that day, so the lyrics got slightly flubbed at one point, but they more than made up for that with their goosebumps-inducing harmonies. Watch a fan-taken video of the song below.

Lucy opens Mitski's "last shows indefinitely" at SummerStage in Central Park this weekend. Saturday night is sold out, but tickets are still on sale for Sunday 9/8.