George was a very clever ukulele player, quite difficult to mimic - the reason why he had his doubters was because there were rumours that he couldn't tune the uke himself, so he had a few on stage with him.

In reality he was such a pro that he was already doing then what a lot of well-respected guitarsists and other string players do nowadays as standard practice - a few instruments in standard or other tunings to save re-tuning in front of the audience, thereby maintaining a slick performance.