If on the left hand side of an accordion you press the C root button and the A minor chord button, you get a C6 chord. Likewise, if you press the C root button and the E minor chord button, you get C major 7. What this means is that if you throw in the obvious C root-C major chord combination, you can play the exciting C major-C6-C major 7 vamp that begins "Begin the Beguine." All on the left hand! Leaving the right hand free for skeetily bop bop, skeeby da doo.