From Wikipedia:
Lindsey Stirling (born on September 21, 1986) is an American violinist, dancer, performance artist, and composer. She presents choreographed violin performances, both live and in music videos found on her YouTube channel, Lindseystomp, which she introduced in 2007. In 2010, Stirling was a quarter-finalist on the fifth season of America's Got Talent, where she was known as the Hip Hop Violinist.
Since 2010, Stirling has released a self-titled album, an EP, and several singles. She performs a variety of music styles, from classical to pop and hip-hop to dubstep. Aside from original work, her discography contains covers of songs by other musicians and various soundtracks.