When playing a polka or jig with repeating Em & D chords, in standard tuning, I substitute a Cmaj7 (332000) for the Em on the 2d time to the Em. Also adding a Bm right after the D gives an interesting sound. Sometimes when playing an A chord I add a x04020 then a x05050 then back to A (x02220) kind of like a run up to x05050 then back down to A. This also works for a blues run. Hope this makes sense. Bill