When the talented Lindsey Sterling is involved in a video, you can bet things are about to get serious. Having brought her own special brand of violin to previous clips like this one, here she's teaming up with musician William Joseph. Who is playing the piano in a flak jacket. If you've ever wanted to see classical music take the place of teabagging in the middle of a Halo firefight, well, now's your chance. You can check out a behind-the-scenes video below. Halo Medley - Firefight - Lindsey Stirling and William Joseph [YouTube]