There's nothing quite like hearing country music echo throughout the walls of a cave. Fans who attended a taping for a Season 9 episode of Bluegrass Underground reveled in that unique experience as Brothers Osborne performed a thrilling, hour-long set inside The Caverns at the base of Monteagle Mountain in Pelham, Tenn.

CMA Award winners John and TJ Osborne took the stage by beckoning the energized audience to get on its feet, and the crowd obliged as they opened with the gritty "Shoot Me Straight" before whisking concertgoers off into the smooth "I Don't Remember Me (Before You)" and "Weed, Whiskey and Willie." The crowd cheered in support for the latter and stood in solidarity for its message: "I've got bottles and vinyl stacked to the ceilin' / I get stoned for survival, it helps with the healin' / And when it all goes to hell, the only thing I believe in / Is weed, whiskey and Willie."

The duo remained in that mellow energy by asking patrons to hold onto one another and sway as they were serenaded with "Tequila Again." Obeying, the crowd became a sea moving in unison to the melody.

"This is my first experience," T.J. Osborne said of being in The Caverns, "and I'm liking it so far."

Brothers Osborne Don't Believe in Staying Quiet

Throughout their eclectic show, Brothers Osborne proved that they're just as strong as musicians as they are singer-songwriters, especially through the revised arrangement of their early hit "21 Summer." While the duo has been performing the fan-favorite for years, they leaned on the cavern's earthy setting for an acoustic rendition that had fans instantly singing along while T.J.'s voice permeated the cave, drawing out the lyrics' emotion in a way that made it feel more like a hallowed moment than a performance.

The Osbornes continued to highlight their musicianship and gift for compelling delivery as they launched into "Stay a Little Longer," which was warmly embraced by the crowd. John kept the energy in motion by urging fans to keep clapping as he played an extended outro solo, citing the venue's pristine acoustics as the reason for his desire to hear their voices echo back to him.

The pair made the rollicking "It Ain't My Fault" even more engaging by passing its signature chant back and forth to the audience, and by turning it into a jam session that lasted well over 10 minutes. The brothers got so lost in the music that they almost seemed to forget the crowd was there, making for an electrifying moment that brought the show to a close.

Brothers Osborne are just one of many acts lined up for the ninth season of PBS' Emmy-winning Bluegrass Underground, which spotlights country, Americana and bluegrass music in a natural setting. Amanda Shires, Nitty Gritty Dirt Band and Steve Earle are all scheduled to appear during the season; Brothers Osborne's episode is now available to stream online, and fans can check local listings for when it will air on PBS.

See Pictures of Brothers Osborne on Bluegrass Underground