I seem to remember Geno Delafose using one many years ago..a pearly white one if I recall....he explained why at a Festival I attended where they had a Q & A session... but now I forget what his answer was...LOL. Also, what does Rosie Ledet play..seem to recall her playing in an unusual key?
Cameron Dupuy has an Eb. Marc Savoy had one but recently sold it. You can hear his on the Back to the Basics CD. It's a bit of an oddball accordion compared to C or D and most traditional Cajun fiddle players will either tune a half step up or down to play with it.