Born on 5 September 1781, Anton Diabelli was a musical entrepreneur who came from an Italian family, but lived and worked in Austria.
He was as much a business man as a musican and his music publishing company (Cappi & Diabelli) became highly successful publishing arrangements of popular opera tunes for amateur pianists. He also recognised the money-making potential of promising young composer Franz Schubert and published the majority of Schubert's works, beginning with his famous Lied "Der Erlkönig" in 1821. He even bought part of Schubert's estate after his death, so that he could continue publishing all the "new", previously unseen works that Schubert had left behind!
The famous "Diabelli Variations" cam about as a result of another money-making idea. In 1819 he called on all of his important composer friends to write a variation each on a little Waltz tune that he had written, as a patriotic celebration of Austrian music. He wrote to all the major Austrian composers, as well as some other important composers from Germany, Hungray and elsewhere. Fifty composers each wrote a variation, including Schubert, Hummel, the 8-year-old Liszt and Czerny (who wrote a coda) and these were published as a set in Diabelli's publication called the "Vaterländischer Künstlerverein" (The Patriotic Collective).
Ludwig van Beethoven also responded to Diabelli's letter, but didn't compose just one variation...he wrote 33! Diabelli published these as their own set, and today they are widely regarded as the finest set of variations ever written.
Listen to Beethoven's set of "33 Variations on a Waltz by Diabelli" and listen to how he varies Diabelli's very simple tune. Unusually most of the variations remain in C major - instead of exploring different keys, Beethoven eke's out the tiny details of the melody.