You may know Dan Tyminski best as a member of Alison Krauss and Union Station or maybe as the owner of George Clooney's singing voice in O Brother, Where Art Thou? And you may know The Travelin' McCourys as the Del McCoury Band minus its patriarch. Well, those two bluegrass worlds collide Friday at HullabaLOU when Tyminski joins The Travelin' McCourys for a set at Churchill Downs on the Bluegrass stage.