Beethoven’s Music Library
After Beethoven died, his estate was auctioned in two parts. The first consisted of his household effects. The second auction, on November 5, 1827, contained his sketches, drafts of incomplete works, autographs of finished works, contrapuntal essays, printed music, and books on music. From the auction catalog, we learn that Beethoven owned many works by other composers, including, for example, Handel’s Messiah arranged by Mozart; Mozart’s operas Idomeneo, Don Giovanni, Cosi fan tutte, and La clemenza di Tito; Mozart’s Requiem and string quartets; Haydn’s oratorios The Creation, The Seasons, and Masses nos. 1 and 3; and Handel’s complete works in the London edition. Single works by other composers such as J.S. Bach, Cherubini, and Paisielo are also inventoried. Missing from the list are any works by one of Bach’s most famous sons, Johann Christoph Bach (1735-1782), who was known as the “London Bach” and famous for own music and for influencing Mozart. In 2004 the antiquarian dealers Ulrich Drüner and Albi Rosenthal sold the American Beethoven Society a printing of Bach’s Sonatas, Opus 17, which, according to Anton Schindler, had been received from Beethoven himself. According to the Beethoven scholar Barry Cooper, there are four inscriptions in the score that appear to have been made by Beethoven himself. This discovery is important, in Dr. Cooper’s words, because it “sheds new light on Beethoven’s knowledge of early keyboard music.”
Treasure 15

Edition of J.C. Bach’s Six Sonatas for the Harpsichord or Piano Forte, Opus 17, (published by J.J. Hummel, Berlin, 1779) with Beethoven’s annotations and an inscription by Anton Schindler.
Gift of the American Beethoven Society
See entry with more details in the Beethoven Gateway
Also on display:

Autograph letter by Anton Schindler, Paris, March 17, 1841
Gift of the American Beethoven Society, 2004
Complete translation
See entry with more details and downloadable image in the Beethoven Gateway.