Carl Philipp Emanuel Bach’s Sonatas with Varied Reprises (comp. 1758–9, publ. 1760) constituted a bold experiment. Spelling out every repeat, Bach applies to each the art of variation. Starting off as a service (“play this and you’ll sound as if you’re improvising”), the opus ends up a masterclass in variation. Tom Beghin, playing his own beloved clavichord, enacts the role of the keyboardist- composer who repeats himself, while never saying the same thing twice.