Just inherited a 120 button piano accordion. What is the purpose of the counter bass? I could understand it if the counter bass to any given button was a fifth apart but why has it evolved the way it has? I'm teaching myself with the aid of some books and a fair understanding of guitar harmony. Doing alright as I've only had it for a week, but the counter bass seems superfluous. Any suggestions as to a use that doesn't involve contortionism of any description?

Cheers Martin