The Library of Congress has deemed him a “national treasure.” He has the ability to hear and comprehend four symphonies in his head at one time. His talent is unfathomable to most people and touches all realms of music, from classical to bluegrass to ragtime to blues. You could tell, though, from his half-closed eyes and rapt expression that ragtime is his true love, as is entertaining an audience. And there was certainly no shortage of entertained audience members at Tuesday night’s performance.