It’s for the belt tension actually! Like a guitar tuner. It’s just one tool in the process though as it is not just the frequency of the belts that matter. Instead the frequency/resonance helps get the belts into similar tension before doing more adjustment.

Spectroid is great! I use it to tune my 3d printer.

Most of them are, but there are non UWP apps on there too.

Yeah, this. Freecad does not count even though it’s slowly getting better. There needs to be industry tools available.

You mean as a prefix, right?

Same. 3?

Have you tried Eternity?