I found a video on youtube by Sarah Savoy, and it seems they are playing it in G.. but G mixolydian, for the melody has that F in it.. so it does seem to be played on the C accordion! But a slowed down version would still be very helpful.
Hey Greg! In the video you found online, David is playing that song in G on his C, so you're right about that. I suggest The Amazing Slowdowner to learn songs--you can slow them down to a note at a time, change the key to anything you want, and it's been hugely helpful as I've been working more on getting better at the accordion over the last year. You don't even need more than the free "trial" version, which will slow down only the first minute or so of any song.
Hey Sarah, thanks for the tip. I'm gettin the hang of it a little bit. The left hand is a lil funky when playing in G. Thanks for the response, your band rocks. Bring them to new mexico!