Theorist, organist, and prolific composer. As a choirboy he learned counterpoint, figured bass, and organ from the local Augustinians. After study at Melk Abbey (from 1749) and at the Jesuit seminary in Vienna (1754), he was employed as organist at Raab in 1755, at Maria Taferl (from 1757), and at Melk (1759-65). In 1791 he became assistant Kapellmeister at St. Stephen's in Vienna; in 1793 he succeeded Leopold Hofmann as Kapellmeister, a post he held until his death.
A master of counterpoint and of the organ, he is perhaps best known as Beethoven's teacher; his advocacy of strict contrapuntal style exerted a strong influence on the fusion of strict and galant styles that characterizes much music of the Viennese classical period. Among his compositions are 300 sacred works, including oratorios and cantatas, and more than 450 instrumental pieces, including symphonies, chamber sonatas, divertimentos, and organ fugues.