Am in process of writing a comprehensive button accordion tutor book covering BC button accordion (sometimes refered to as a melodeon) and also the BCC# box with accordion bass as played by the late Sir Jimmy Shand and also by John Kirkpatrick.
The BCC# is the natural box for BC players to move onto if they require a full accordion sound and is also a more natural progression for DG melodeon /diatonic accordion players than is a piano accordion.

Would appreciate any comments/ideas as to what to include/leave out etc.