As David Letterman draws closers to his final show on May 20, each of his musical guests have consistently hit it out of the park. Such was the case last night (May 4) when the Avett Brothers and Brandi Carlile teamed up for their own rendition of the folk classic, “Keep on the Sunny Side.”

Carlile takes the lead on the song, with brothers Seth and Scott Avett supporting her for powerful harmonies. Check out the performance in the video above.

Iron and Wine and Band of Horses’ Ben Bridwell, Elvis Costello and Jason Isbell and Amanda Shires have already acted as a handful of Letterman’s musical guests in the last stretch of his Late Show tenure. Still to come are Mumford and Sons, Tom Waits and more.

Carlile dropped her most recent full-length, The Firewatcher’s Daughter, back in March. While she didn’t treat The Late Show audience to a song from her latest LP, she did when she visited Conan for a performance of "Wherever Is Your Heart.”

It’s been a couple of years since the Avett Brothers released their 2013 album, Magpie and the Dandelion, however, Seth Avett has been keeping busy with various side projects. Avett recently recorded a cover of Blind Melon’s “St. Andrew’s Fall” in support of an upcoming documentary detailing the life and work of the late frontman Shannon Hoon. Avett also dropped an Elliott Smith tribute album with singer-songwriter Jesica Lea Mayfield earlier this year.

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