I'm sure many Hayden/Wicki aficionados would say "yes", but it is not my intention to re-open that debate! I'm prompted by the posting of this unusual duet. It's similar to the Wheatstone duet (but with five columns instead of four) and to the continental (or "chromatic") button accordion (and Tona's custom concertina, with three rows (rather than columns) arranged by the same principle). I'll refer to it as the Five Column Chromatic system, or 5CC for short (making the Wheatstone duet the 4CC s