So I've been playing some trad-jazz (actually, a lot of it). Usually I've been playing in two, except the occasional chorus in four, or maybe just the bridge in four, or the last 8 in four, or a shout chorus in four. But mostly in two. I have recently found two videos that from the production values I guess were filmed in the 50s or early 60s. One of Eddie Condon and one of Bobby Hackett. They are playing trad standards with a typical trad front line (clarinet, cornet/trumpet, trombone), piano, drums, bass. Now the surprise to me: The bass is playing in four pretty much all the way through, constantly. Can anyone comment? did the trad guys move to walking in four in the 1940s-50s like everyone else? Was playing in four a Chicago thing and the N.O. guys stayed in two? What am I missing? I don't even know the questions to ask!