Who is Sir Rosevelt? Whoever they are, they're filling Twitter with a campaign asking that question (#WhoIsSirRosevelt), and there's only one thing we know for sure: Zac Brown is heading up this mysterious side project.

As Rolling Stone first reported, Sir Rosevelt is "the name of the mysterious new group whose members are anonymous -- at least for now."

The only other thing we know for now is their sound: the group just released their debut song "Sunday Finest." Not surprisingly for a project involving Zac Brown, the song is a cross-genre dance romp suitable for play on pop, country, R&B and oldies stations.

Sir Rosevelt's website is equally cryptic, featuring only what Rolling Stone accurately describes as "two burly, shirtless men flanking a Lana Del Ray lookalike" while "Sunday Finest" plays in the background.

Maybe Zac Brown wanted a chance to branch out into other genres, as Zac Brown Band recently announced that their next project will be a return to their country roots.

You can catch the group at their last 2016 show in Fayetteville, Ga. Proceeds from the show will benefit Camp Southern Ground, a camp for children ages 7-17 with "special emphasis on children with Autism Spectrum Disorders (ASD), learning and attention issues, social or emotional challenges and those with family members serving in the military."

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