The Castagnari Lilly is perhaps the most famous one voice melodeon on the market. Beautifully made the Lilly is light and compact, but don't let its size fool you, it packs a lot of punch. Fast and responsive the Lilly has been found in sessions, morris sides, with singers etc for many years.
21 buttons with a stepped keyboard it is matched by an 8 bass left hand. The buttons are smaller than you find on larger instruments, but this doesn't make it any harder to play.