The vids show accordions with the Free-Bass system as opposed to the most common Stradella Bass system. Here are a couple of examples of the same piece using the Free-Bass system. The first vid is Uwe (Oove) Steger, the same guy in the other vids. The second is my friend Joe Natoli using a harpsichord sound rather than traditional accordion sound on a piano keyboard accordion:
http://www.youtube.com/watch?v=yKxI_mOHoQw&feature=related

http://www.youtube.com/watch?v=v19edtyl8lo&feature=related