Rex Lewis-Clack, who is on the autism spectrum, has exceptional musical abilities. Patrick Fallon / Spectrum News “It don’t mean a thing if it ain’t got that swing,” Rex Lewis-Clack croons, his head joyfully bobbing in time with the Duke Ellington standard. The 20-year-old musician accompanies himself on a grand piano, deftly striking the keys with a dexterity reminiscent of the Duke himself.