I attended a talk by the guy who built this thing: http://web.cecs.pdx.edu/~harry/Relay/

He included a live demo. It made a very satisfying "kachunk-kachunk-kachunk" sound as it multiplied two numbers. It also made me realize that the threshold of complexity necessary to construct a practical turing-complee computing device is quite low.

Indeed, it doubled as a beatbox machine, with 99% perfect rhythm! https://www.youtube.com/watch?v=n3wPBcmSb2U

(Unfortunately the small demo isn't doesn't run to completion, perhaps because the source material didn't include it, or because uploading it all would have been nontrivial)