There's always a family atmosphere at a Keimzeit concert. Over the decades, the band from Potsdam has built up a cult following with a brand of rootsy, melancholy guitar pop that once earned them the moniker "the Grateful Dead of East Germany."

At a recent gig at the Kulturbrauerei venue in Berlin, they brought along a special guest. For many, she stole the show. Joining them on stage was Laura Schwengber, a sign language interpreter. It's the second time she's appeared in Keimzeit's traditional end-of-the-year performance and their fans welcomed her into the fold.

"Last year, we didn't publicize my role because the organizers had some concerns about how I'd be received," explains Schwengber.

Keimzeit had long been interested in the idea of using a sign language interpreter after a friend of the band had lost his hearing, but found that most venues weren't willing to play along.

"They raised all sorts of objections, saying that an extra person wouldn't fit on stage, that it would distract from the band, that it would turn the event into a show just for disabled people," says Schwengber. "The organizers were basically worried what the reaction would be."

Connecting with sound

They needn't have been. On stage with Keimzeit, she does far more than interpret their lyrics, throwing herself into her task with an energy that would make Beyoncé look tired, and communicating the entire musical experience of a live show - audience clapping and sing-alongs included. As well as signing, she dances, mouths the lyrics, plays air guitar, mimes drumming and blowing a trumpet, and even conveys the effect of a wah-wah pedal.

"What I want to do is give deaf people the same sense of being blown away by a gig that others have," says Schwengber. And though someone who is deaf or hearing-impaired might experience a rock concert differently, its impact is no less immediate.

With her expressive, animated signing, Laura helps them connect with the sound. To the deaf and the hearing-impaired, this doesn't only happen via the ear. To them, the body can function like a resonating chamber, allowing them to feel the vibrations of loud music. Visuals also help.

In a TED talk in 2007, the deaf Scottish virtuoso percussionist Evelyn Glennie shared her views on "how to truly listen."

"Can you hear anything?" she asked the audience, holding her sticks just above her snare drum. "No. Exactly. Because I'm not even touching it. But yet, we get the sensation of something happening. In the same way that when I see a tree move, then I imagine that tree making a rustling sound. Whatever the eye sees, then there's always sound happening."

An evolving language

A qualified sign language interpreter, Schwengber is now pursuing a Bachelor's degree in Deaf Studies (Language and Culture of the Deaf Community) at the Humboldt University in Berlin, the only course of its kind in the country.

Home to about 80,000 people categorized as deaf and 16 million who are hearing-impaired, Germany didn't officially recognize sign language until 2001. These days, approximately 200,000 people use German sign language (DGS), and as Schwengber points out, it's still evolving.

"There needs to be much more work done on aspects of the language such as slang and dialects," she says.

She's a bit too busy for research herself, however. Since she debuted with Keimzeit in 2012, her dance card has been filling up fast. In November, she appeared with German band Selig and the German Film Orchestra Babelsberg and in late December she accompanied a production for children of "Peter and the Wolf" in Potsdam.

In collaboration with public broadcaster NDR, she has also supplied a series of highly popular sign language interpretations for a range of music videos, including German soul star Xavier Naidoo and rapper Cro.

"He was difficult," says Schwengber of Cro. "It's easier when the musicians I'm interpreting use a lot of imagery, and rap tends to be factual."

An added attraction

Although part of what she does on stage is intuitive - and she inevitably has to be ready to improvise, too - Schwengber prepares for shows meticulously, closely studying the band's music and lyrics. While the members of the band might take a quick break backstage now and then, she is in the spotlight for every second of the evening.

"I usually have sore muscles the next day and I keep resolving to do more sport to boost my stamina," she says with a laugh.

Considering that demand for her job is on the rise, bulking up may not be a bad idea. Bands in the US pioneered the use of sign language interpreters, and these days, they're a regular fixture at most of the big music festivals, appearing with headliners from the Rolling Stones to Green Day and the Wu-Tang Clan. And as Eddie Vedder of Pearl Jam said way back in 2000, "they're much more interesting to watch than any of us."

The audience at the recent Keimzeit show was certainly intrigued. "It was a great experience, and I was also positively surprised by how many people asked me about deafness and sign language afterwards," says Maren Kirschke, who has been deaf since she was 14. "A sign language interpreter on stage is an added attraction, even for people who can hear."

On YouTube: Laura Schwengber signs with Norbert Leisegang from Keimzeit