The Swell Season performed at Warehouse Live in Houston on November 13, and according to the description on the YouTube tag:
Glen introduced a new song, inviting the audience to sing along. Upon a quick rehearsal of our part, he heard one voice that he dubbed "Aretha" and promptly invited it's owner, Moji to join him onstage. Here is the magical result!
I love when she cues the band to come back in with louder dynamics. She's obviously a pro.
Moji's band: the 2 Dollar Sound