I always liked Pete Seeger. Very versatile and intelligent

I used to wonder why more of the techniques he used you didn't hear many other people use.

That 6/8 thing he used to do the Irish Washerwoman with - you never actually hear an Irish band use that although it sounds very good.

That version of Blue Skies on the Goofing Off Suite - you don't hear many people do that.

Finally I loved his understanding of accompaniment - all that fretless slidey stuff.