He's just strumming the air!
Building An All Plastic ‘0% Wood’ Acoustic Guitar

In a step towards playing air guitar and actually having sound come out and shock the people watching, this is a video of Tim Sway attempting to build a ‘0% wood’ acoustic guitar, constructed almost entirely out of clear acrylic plastic with metal hardware. But how does it sound — that’s the question. And the answer is not bad. Now carve one out of solid marble! Then we can hang it around the neck of Michelangelo’s David like he’s a rock star. Plus it’ll cover that little dangle of his so I can stop staring at it. Really draws the eye, doesn’t it? It’s like the middle of a dart board.