Playing in the Austin High School Marching Band has always been cool….but it just got a whole lot cooler. For the second time, the award winning high school band shared the stage with Mumford and Sons, backing the band on their biggest hit, “The Cave.”

The free Myspace show on the University of Texas campus Saturday night followed a screening of a documentary film that had its world premiere, hours earlier, at SXSW. Emmett Malloy’s Big Easy Express takes you on board with Mumford and Sons, Edward Sharpe and the Magnetic Zeros and Old Crow Medicine Show during their train tour of six cities last year – a tour that brought them into Austin and into the lives of some teenage musicians whose audience is typically gathered at House Park for a Friday night football game.

Austin High School Band Director Brian Frock says he doesn’t really know how it came to happen that the band he leads got the opportunity to play with the most popular folk-rock band out there. Last April, after a series of phone calls and rehearsals, the AHS Band welcomed the members of Mumford and Sons to the Austin High band hall.

Haley Barlow plays clarinet and is currently one of three drum majors in the AHS Band. “It was almost surreal spending time with Mumford and Sons last year. They seemed almost out of place in our band hall, which many of us practically live in. Mumford and Sons are very, very laid-back guys. . .They are just living and loving life. They got the biggest kick out of seeing us just playing our warm-ups.”

Frock adds, “They were amazing. They treated our kids like we were the stars of the show. It was at the end of that rehearsal that they invited us to join them that evening on stage as part of their show. It was the most amazing experience!”

That rehearsal in the band hall and the AHS Band’s performance on stage during the Railroad Revival Tour stop in Austin last year are featured during a 4-5 minute portion of the documentary about the tour; Big Easy Express.

A few weeks ago, another phone call the AHS Band had been waiting for came – Mumford and Sons asked them to play with them again during SXSW.

“The kids were pumped to say the least. We've hoped since last year that we'd be contacted again,” Frock says.

“When I heard we would be playing with them again, I freaked out!” Barlow exclaims.

Friday night, the AHS Band rehearsed once again with Mumford and Sons and were treated to a private screening of Big Easy Express. “It was so exciting both to see ourselves on this huge blow-up screen and to just relive the experience,” Barlow says. “It all came back so vividly seeing it on screen. Everyone was pointing themselves out on screen and laughing.”

Thousands of people gathered on the lawn near the LBJ Library on the UT campus Saturday to be part of a free event unlike any other during SXSW. The crowd watched Big Easy Express, before rising to its feet for an energy-packed show that included Edward Sharpe and the Magnetic Zeros, Mumford and Sons, members of Old Crow Medicine Show and of course the act that got the loudest applause of the night — the Austin High School Marching Band.

“It's awesome for our kids to play for this type of crowd. High School bands typically play for a football crowd. This is totally different. The crowds are very enthusiastic,” Frock says.

No doubt Austin High School will be abuzz about this when the school bell rings again on Monday. While some kids spent their March Break at the beach or hanging with friends, some young musicians took the world stage once again, backing one of the biggest bands in music today.