If you’ve been to Austin City Limits Music Fest, you’ve seen them. And while they’re not the band, they are on stage and they are very talented, in their own way.

They've worked with everyone from Wu-Tang Clan to Green Day, from Black Sabbath to Jack White. They even braved the harsh cold of President Obama’s 2012 inauguration this past January.

They’re the sign language interpreters of LotuSIGN, and you can find them emphatically interpreting bands' lyrics and sounds at performances across the country. And while there’s plenty of air guitar and air piano, LotuSIGN means business.

The company specializes in providing deaf and hearing impaired festival-goers the chance to experience live music. LotuSIGN founder Barbie Parker says she and her fellow interpreters weather any event rain or shine, which she expects to be a factor at this weekend’s ACL Fest.

“We prepare for everything. We did the inauguration this year when it was in the 20’s, working without gloves, and we did festivals as hot as 108 degrees this summer,”Parker says. “This is what we do.”

And that’s what Parker has been doing since 2000. A few years after she got involved with ACL , when she began contracting local interpreters and volunteers to work the fest. It was tough-going, at first, Parker says. There isn’t exactly a manual for interpreting a searing guitar solo or an electronic dance music set. It requires intuition that’s hard to teach.

“It’s live music [and] it’s something that’s completely different,” Parker says. “People are taught to dance, but some people can’t dance well naturally…we’re the first real company that’s doing this and we’re doing this for huge crowds.”

Since then, Parker founded LotuSIGN in 2009 and they’ve expanded – working South By Southwest, Lollapalooza and Orion Fest, as well as being featured in The New York Times and on The Today Show. Last weekend interpreter Lucy Brotherton even got a shout out from Wilco's Jeff Tweedy.

Parker has enjoyed the nods, but she said it’s not about the stage time: It’s about the business and helping deaf audiences enjoy the experience.

“It brings attention to the work we do,” Parker says. “But it’s never about the interpreter or how popular we are. It’s about the access and we make sure that’s available for deaf audiences.”

Here’s a short video produced for ACL Fest 2010 about LotuSIGN:

Watch LotusSIGN founder Barbie Parker rock out with Green Day frontman Billie Joe Armstrong:

LotuSIGN achieved viral success this summer when interpreter Amber Galloway Gallego signed for rapper Kendrick Lamar. (The language may not be safe for your workplace.):