I almost wish I had left this thread alone so that Rick's praise of Frank H (with which I totally agree!) could stand alone, but I gotta spend some time agreeing with those who praise Pete S.

1) He could do bum-titty better than ANYBODY else I know, and used that strum to back up an astonishingly large number of songs. Very well.
1a) the only other person I know who REALLY got into the bum-titty strum was the late Peter Colby of Brockton MA, who used it to back up contradance fiddle (and accordion).

2) he could play any number of other styles very well: frailing, up-picking, various three-finger styles; about the only thing I've never heard him do is Charlie Poole's style (as a Poole freak, I listen for it) and had a gift for finding exactly the right style to express what he wanted to.
2a) somebody pointed out that accompaniment to "come all ye fair & tender ladies" from Darling Corey-- agreed. WOW.
2b) some of his experiments on Goofing Off Suite-- just thinking of them in the first place was a wonderment, then DOING them. . .
2c) on the various American Favorite Ballads (didn't it get up to volume 4?)-- the accompaniment ALWAYS fit the song being sung. WOW.
2d) and he had a gift for making OTHER people sound wonderful, as has been pointed out already

3) Where I disagree with Rick: he cites "number of keys used" as a point in Pete's favor-- not sure this is relevant. With a long neck banjo in G tuning you can play in any key from E up to C; in C tuning from A to F; you pitch the song where it suits your voice once you've learned this is a good idea.
3a) but Pete COULD play well in any number of tunings; can't even count all the tunings he used on Goofing Off Suite alone!

4) I wonder if anybody else of my generation (tried to learn banjo from the YELLOW edition of "How to Play. . . " starting in 1960) had the same experience I did: the "basic strum" bum-titty was one I found to be a musical dead end! I played basic strum for about two years anhd had a great deal of trouble unlearning it when I learned to frail-- IMHO you can do everything with frailing that you can with bum-tty and it's a lot more versatile once you get into double-thumbing and moving the thumb off the 5th string. And the 2nd edition's description os Scruggs style-- ouch! (by the time the 3rd edition and its red cover arrived-- MUCH better!)

5) to summarize: a wonderful musician and, not unmindful of Earl Scruggs and Don Reno, probably the best banjo player of his generation. Not a bad guitar player (6 and 12 string!) or mandolin player either! ANd I will always be grateful to Seeger for that little squib in that book I just complained about mentioning the late Paul Cadwell, classical banjo player who I was sure had three hands, until I actually met him.