Tracing the history of that "marvelous music machine" in conjunction with the Smithsonian exhibition "Piano 300: Three Centuries of People and Pianos." The tuneful hour (composers include Bach and Ellington) explores the development of the piano from its invention in 1700 by Florentine Bartolomeo Cristofori. One "active fomenter" of its development, says pianist Robert Levin, was Beethoven. "He wanted more power. He wanted more notes. He wanted it to go higher. He wanted it to go lower."