Beethoven's most famous works include the Sonata, which is a type of musical composition for one or two instruments, usually in several movements. His most famous Sonata is the 'Moonlight Sonata', which was composed in 1801 and is one of the most popular pieces of classical music. Additionally, Beethoven wrote nine symphonies, 32 piano sonatas, and 16 string quartets, all of which are referred to as Opuses.