In following Larry's suggestion to "add 1 letter to the c notes", it would be the E that becomes F sharp, and the B that becomes C sharp. I think Larry was highlighting that there is no F or C on a D box, as there is on a C box.
I could also import Dirk's video into the computer and speed it up a tad so it matches the pitch of the box. BUT, my uncle that has the thing hasn't show up with it yet so I'm not crossing fingers for it. If that falls through I'll just find a C box and not have to worry about speeding up the music.
Re: Martin D accordion/Free Tempo and Pitch Change Software
I've used Sound Forge to edit sound files. It will change tempo without changing pitch, change pitch with changing tempo, etc. It was affordable on eBay. But there's legitimate free software that does many of the same tasks:
Audacity is one of the open source projects, and is supposed to be reliable. I think it has an optional free mp3 encoder, too.
I've found this software great (1) to slow down fast licks, and (2) to place a song in a key I can play on my C or B-flat.