“Standards are cruelly high at the top,” George Harrison observed in a May 1965 interview. “Every time we get a record released, it has to go to No. 1.  If it doesn’t, we’ll be slipping.”  Today, we take for granted that The Beatles certainly didn’t slip.  Just months later, on October 12, the group started sessions for what would become their sixth original U.K. studio album: Rubber Soul.  Yet more than just charting further No. 1s – the album itself went to that position in both the U.K. and U.S., and the…