“We’re basically rock ‘n’ roll bluegrass for lack of a better term,” says David Mayfield, guitarist of Cadillac Sky. The band will open the sold out Mumford and Sons show at the Republic tonight, and another term he likes to use is “alt bluegrass.” Whatever they call their genre, Cadillac Sky creates a sound that appeals to lovers of country, bluegrass, rock, and everything in between.

The band is made up of Mayfield on guitar, mandolin and drums; Matt Menefee on banjo, piano, and drums; Andy “Panda” Moritz on bass; Ross Holmes on fiddle and guitar; and newest member Levi Lowry on guitar and violin. All of the members lend their voices and their stories, along with their traditional bluegrass instruments and their modern rock instruments.

Cadillac Sky not only stands out with its sound, but also with its recording process. The band recorded its newest album, Letters in the Deep, with no computers. The record was produced by Dan Auerbach of the Black Keys, and they tried to stay away from that “polished” sound.

“We basically sat in a circle with no headphones on and two or three microphones set up. And we just played,” says Mayfield. They sang all the harmonies on one microphone, used tape machines and vintage microphones, and did only minimal dubbing afterward. “There [are] lots of mistakes on that record, but it’s real. And that’s what we sound like.”

While going old school with the recording process, the group also went to their pasts for their songs. “On the newest record, I think every single song comes from a very personal place,” he says. Mayfield’s songs were about past relationships, failed engagements, and “pushing on when the struggles of everyday life get to be a little too much.”

Cadillac Sky and King Charles will open for Mumford and Sons at Republic tonight. The show sold out weeks ago.