It was Ray Whitley who started the excitement. Throughout the 1930s, Whitley traveled with the World’s Championship Rodeo, providing musical entertainment with his band, the Six Bar Cowboys. In 1937, he prodded the Gibson Mandolin-Guitar Manufacturing Co. to develop a “super jumbo” instrument, one that could go lick for lick with the nearly 16-inch-wide, rosewood-and-mahogany…