Want to start your day on a high note? We've got just the thing -- Jason Momoa shredding a guitar shirtless in the California desert!

The "Aquaman" star ditched his top while joining his band, ÖOF TATATÁ, for a sound check at The Red Dog in Pioneertown ... and if the abs didn't grab your attention, his guitar skills probably did.

Jason was spotted entertaining a crowd that gathered to catch the rehearsal ahead of the group's limited West Coast run, turning a simple sound check into its own mini show.

And let's be honest -- he's long committed to the rocker aesthetic these days, complete with the beard that has made a triumphant comeback after the dramatic shave that shocked fans last year.

BTW, he did throw on a shirt during the actual set later in the day -- jamming out for a group of fans while playing some Red Hot Chili Peppers.

Rock on, Jason!