fluffy
If you've ever played both a bass and a guitar, you'd know why an upright bass would work but an upright guitar wouldn't.

Lurchi
By the way this is one of the best things I've ever seen/heard.

Syd Midnight
The upright bass was still an orchestral instrument like the cello and viola, totally unrelated to guitars. Electric bass wasn't even invented until the late 50s, and they are considered a type of guitar.

It's a shame they were so difficult to record on crappy old studio equipment, I love upright rock bass.