An all accordion marching band... yikes! Allthough that could go over big in Green Bay during the halftime of a Packer game. An accordion has got to be easier to play than a horn instrument when it's -10 degrees.
In Milwaukee they have the Riverwest Accordion Club. Although not a marching band, they're numbers sometimes reach 10 or 15 accordion players all attempting to play at once. It sometimes sounds like a large bag of cats in a cement mixer, but othertimes the synergy comes together and they can sound pretty neat. They're specialty is a melody of beer jingles from old commercials. Great stuff.
The Riverwest gang is a real rag-tag bunch with many more amatuers than real musicians, but no one really cares about that and everyone has a great time. I get the impression that they don't really rehearse, people just sort of show and play. A couple of summers ago, the Riverwest folks opened for TDA at Onapa Brewery. A great night of acccordion madness.