WALDSTEIN, FERDINAND, COUNT ( I , the youngest son of Graf Waldstein and Wartemburg von Lux, was born on March 24, 1762. At Bonn, Beethoven received encourage ment from this young nobleman, whom he immortalized by dedi cating to him his opus 53, afterwards known as the "Waldstein" sonata. A theme of Count Waldstein's also served for a set of 12 variations for piano duet, written by Beethoven in 1791 or 1792. Waldstein died on Aug. 29, 1823.