Flemish comedian and avid DIY builder Henk Rijckaert has posted the instructions on how to build your own "Tennis Rock-it":
Sooner or later, every child pretends that his tennis racket is a real-life guitar that you can actually play. Imagining endless encores, we all play on the stage of our bunk bed for screaming audiences going wild.
That’s why I made this tennis racket into an electric guitar: as a noisy tribute to the ten year old boy standing in front of the mirror, jamming on air and dreaming of being the next guitar hero.
Full instruction (in Flemish) here.