Justin Vernon of Bon Iver fame is producing English folk trio the Staves‘ second album, If I Was. Vernon must’ve felt the need to come out from behind the scenes, though, because he joined the ladies onstage Thursday night at a concert at Hackney Empire in London. They played “Make It Holy,” a track from the upcoming album that hasn’t officially been released yet, and Vernon provided backing vocals and a little extra guitar. “Music is the most amazing thing,” the Staves’ Emily Staveley-Taylor said as Vernon left the stage after the song ended. “[It] has let us meet the most incredible people. It’s magic.” Watch a fan-shot video above, and wait for If I Was to come out on March 31 if you’re so inclined.