literature. The études of op. 97, Études dans le genre fugué, published in Paris by 1817, are similarly advanced. Each composition is preceded by Reicha's comments for young composers. Thirty of the 34 études included are fugues, and every étude is preceded by a prelude based on a particular technical or compositional problem. Again an exceptionally large number of forms and textures is used, including, for example, the variation form with extensive use of invertible counterpoint (no. 3), or an Andante in C minor based on the famous Folia harmonic progression. Reicha's massive cycle of variations, L'art de varier, uses the same pedagogical principle and includes variations in the form of four-voice fugues, program music variations, toccata-like hand-crossing variations, etc., foreshadowing in many aspects not only Beethoven's Diabelli Variations, but also works by Schubert, Wagner and Debussy. Many of Reicha's string quartets are similarly advanced, and also anticipate numerous later developments. The eight Vienna string quartets (1801–1805) are among his most important works. Though largely ignored since Reicha's death, they were highly influential during his lifetime and left their mark on the quartets of Beethoven and Schubert, much as Bach's Well-Tempered Clavier was ignored by the public but well known to Beethoven and Chopin. Reicha also wrote prolifically for various kinds of ensembles other than wind quintets and string quartets, including violin sonatas, piano trios, horn trios, flute quartets, various works for solo wind or string instruments accompanied by strings, and works for voice. He also wrote in larger-scale genres, including at least eight known symphonies, seven operas, and choral works such as a Requiem. Much of Reicha's music remained unpublished and/or unperformed during his life, and virtually all of it fell into obscurity after his death. This is partly explained by Reicha's own decisions he reflected on in his autobiography: "Many of my works have never been heard because of my aversion to seeking performances [...] I counted the time spent in such efforts as lost, and preferred to remain at my desk." He also frequently advocated ideas, such as the use of quarter tones, that were too far ahead of his time to be understood by his contemporaries. Writings Reicha's major theoretical and pedagogical works include the following: Practische Beispiele: ein Beitrag zur Geistescultur des Tonsetzers ... begleitet mit philosophisch-practischen Anmerkungen (1803), a didactic work that includes 25 sight-reading exercises of extreme difficulty, some of which were later