When Texas Playboys front man Jason Roberts steps onto a stage with his fiddle and utters his first “AH-ha” of the evening, western-swing fans know they’re seeing and hearing nothing less than the living embodiment of a tradition that stretches all the way back to 1933. That was the year the charismatic fiddler Bob Wills and several other musicians in a group called the Light Crust Doughboys broke away from Fort Worth’s Burris Mills and its autocratic business manager, W. Lee “Pappy” O’Daniel, to form their own band. As Bob Wills and His Texas Pla