Brandi Carlile writes some beautiful songs, but she’s also really great at performing other people’s music. In the past few months, Carlile has taken on songs from people like Tom Petty, Soundgarden, John Denver, and John Prine. Last night, as a guest on Stephen Colbert’s Late Show, she also busted out the Joni Mitchell classic “A Case Of You.”

Carlile was on Colbert because she’s just written a new memoir called Broken Horses. With her appearance on Colbert last night, Carlile made the leap from musical guest to interview subject. She talked to Colbert about John Prine and about the conflicts between her religious faith and some traumatic moments that she’s had in the church. It’s one of those Colbert interviews where nobody does bits, where they just cannonball straight into the deep end.

During the interview, Colbert brought up Joni Mitchell, a friend of Carlile, and this led to Carlile picking up an acoustic guitar and singing Mitchell’s 1971 song “A Case Of You.” (Carlile once covered Mitchell’s entire Blue album in front of Mitchell herself.) This didn’t exactly happen in the course of natural conversation, but it’s still a cool moment, like when Dolly Parton sang for Colbert and made him cry. Below, watch the interview and the performance, and listen to Mitchell’s original “A Case Of You.”

Carlile’s book Broken Horses is out now, via Crown Books.