He is best known as a session musician, having performed on recordings by Kid Rock, the Avett Brothers, Conor Oberst, Norah Jones, Dixie Chicks, Zucchero, P!nk, Lana Del Rey, Dangermouse, Paulo Nutini, and Weezer.

Mills began his musical career as a founding member of Simon Dawes with Taylor Goldsmith. They recorded and released the EP What No One Hears in 2005, and the 2006 full-length Carnivore.

After he left, the band shortened its name to Dawes. Mills became a touring guitarist for Jenny Lewis. He also served as a hired gun for Band of Horses, Lucinda Williams, and Julian Casablancas.

Until that time, Mills never really considered himself a solo artist. His first recording on his own, Break Mirrors, was released with the intention of securing more session work and becoming a producer. The end result was widely acclaimed for its overall originality in writing, arranging, and producing.

His strategy worked. He co-produced Jesca Hoop's The House That Jack Built in 2011, and produced fiddler Sarah Watkins sophomore release, Sun Midnight Sun. He produced, co-produced, and/or played on several tracks by several other musicians as well as contributing to compilations. His co-production and performance of "Oh Well," with Billy Gibbons and Matt Sweeney, on the tribute album Just Tell Me That You Want Me: A Tribute to Fleetwood Mac, was considered by many the set's highlight.

Mills began recording his sophomore offering Heigh Ho at Capitol's Ocean Way studio (the room was built for Frank Sinatra), with a host of guests that included Fiona Apple, Jon Brion, Benmont Tench, Don Was, and Jim Keltner. The album was released in September of 2014. ~ Thom Jurek