I've just taken up the freebass. I changed from piano accordion to C-system button freebass convertor with buttons on both hands. There seems to be two common types of Freebass system based on the two common types of button accordion. C-system from Central Europe e.g. Italy, and B-system from Eastern Europe e.g. Russia. There are some less well know variations on these specific to Finland/Sweden/Balkans which I was advised to avoid. The left hand of the common C-system freebass is a mirror image of the right hand buttons. The left hand of the B-system freebass is as if the buttons have been rotated through 180˚, i.e. the low notes are nearest the chin on the right hand and nearest the floor on the left hand. I chose the C-system because the hands mirror each other which made me think it might be easier to learn and because the French chromatic Peguri bandoneons which I would also like to learn are most similar to the C-system. Good luck. Have fun.