Oh dear, I hit "submit" before I had finished the previous post. I am doing this on my netbook and the keyboard is rather cramped.

To continue, going back to the accordion question, leaving out the thirds on an instrument with limited chords on the left hand makes sense as it gives more choices as it is possible to complete the chord on the right hand. I know a PA player who plays the right hand chordally and only uses the left hand for basses. This is on a 12 bass PA. On some melodeons there is a stop which takes out the thirds from the left hand chords.