Hi..
I'm Peter, live musician, with "perfect pitch", experienced audio-freelancer, working with exactly same to yours projects..
pls check in my portfolio demo example of old Polish song (with really pure quality audio source) converted to piano part as mp3 and score...
Thank you for all details in your project description, all attached files - I checked them - I can provide for you requested work.
..what I need to ask - is - do you want "Left Hand" of accordion/s/ part/s/ written as score - or - as chords sequences (both versions are available, and both versions are popular by accordionists - as I remember from few years "live play with my band in Germany: "polkas, Stimmungs" as Rosamunde, and another were our "daily repertoire)
let`s chat about those details - and let`s go..
rgds
Peter..
/"let the accordions play Polkas"/