I'm actually not sure how to go about searching for a primer on what seems to be a simple topic. (Excepting my math skills have seriously slipped, it's been a while!)

Doing conversions between percentage of semitone, playrate, and hertz.

Should be easy, I just seem to have cotton in my brain and can't wrap my head around it. That's where a primer would come in handy. I don't want to be reliant on an internet calculator widget to do this work.

What triggered this, in particular, is I have a excellently horrible kids toy electric keyboard (shaped like an alligator!) that sounds so fucking awful it's brilliant! I rigged up a line out, lovely! It consistently plays everything 32% of a semitone flat! This is nicht gut! So I'd like to slow my daw (Reaper, in this case) by an amount to match. Reaper measures this in percentage of playrate.

But again, overall, I'd love to learn all the conversions.

So, do you know where I'd find such a primer?