Ludwig van Beethoven, Brief an Karl Holz in Wien, Baden, 15. August 1825, Autograph

In 1824 Karl Holz became the second violinist in the Schuppanzigh Quartet (which is why Beethoven addresses him as "Beste Violine 2do") and as a result became friends with Beethoven. As with many of his close friends, Holz also performed everyday services for the composer and worked as his unpaid secretary. Beethoven and Holz had a deep affection for each other. Together with the cellist Joseph Linke, Holz had copied out the parts of Beethoven's String Quartet op. 132 from the autograph score in August 1825. At the time Beethoven was in Baden and gave the corrected copy to his nephew Karl when he came to visit. He sent his friend Holz a letter containing his corrections and explained single changes in detail.