Actually, I'm a bass player but it's quite common that as a bass player you have an accordion as a second instrument because the accordion bass is tuned in fifths like a bass so you get the bass side for free :) Personally, I always play by ear or after chord analysis and I like when I find videos when there is no bass player so that I can play along because it is the best training you can get when you are learning to be responsive. Here is I will Survive together with some street musicians who have a drummer but lack a bass player.