Beethoven never called it the Moonlight Sonata, never pictured a lake at night, and never intended to dedicate it to Countess Giulietta Guicciardi. This episode traces the accidental biography of Piano Sonata No. 14, Opus 27 No. 2, composed in 1801 and published in 1802. Beethoven had planned to give Giulietta a lively rondo in G major, owed that piece to another noblewoman instead, and handed his student the sonata sitting on his desk as a backup gift. The famous nickname came in 1824 from critic Ludwig Rellstab's poetic description of a moonlit lake, and the Lake Lucerne connection was added later by Wilhelm von Lenz, something Rellstab never wrote.

We dig into what Beethoven actually built: a sonata in the manner of a fantasy that inverted the fast-slow-fast template into an end-weighted journey from a hypnotic C-sharp minor adagio to a  ...