I don't think the main influence on the Beatles use of different chords was folk or skiffle. In Hamburg they found themselves learning tunes like "Besame Mucho" and "Till There Was You," and others, so as to service the servicemen. If you listen to the Beatles "Live at the BBC", they were magpies.

(Thanks M.Ted, you are sure right about Harry Partch records, no one has them anywhere -- have to get them online. But thanks for the tips.)

yours,

Peter T.