From Wikipedia: The 'Große Fuge' (or 'Grosse Fuge', also known in English as 'Great Fugue' or 'Grand Fugue'), Op. 133, is a single-movement composition for string quartet by Ludwig van Beethoven. A massive double fugue, it originally served as the final movement of his Quartet No. 13 in B♭ major (Op. 130) but he replaced the fugue with a new finale and published the Grosse Fuge separately in 1827 as Op. 133. It was composed in 1825, when Beethoven was completely deaf, and is considered to be part of his set of late quartets. It was first performed in 1826, as the finale of the B♭ quartet, by the Schuppanzigh Quartet.
The Große Fuge is famous for its extreme technical demands and its unrelentingly introspective nature,[1] even by the standards of his late period. It is the largest and most difficult of all of Beethoven's string quartet movements.[2]
Most 19th century critics dismissed the work. Daniel Gregory Mason called it "repellent",[3] a reviewer writing for Allgemeine musikalische Zeitung in 1826 described the fugue as "incomprehensible, like Chinese" and "a confusion of Babel".[4] However critical opinion of the work has risen steadily since the beginning of the 20th century. The work is now considered among Beethoven's greatest achievements. Igor Stravinsky said of it, "[it is] an absolutely contemporary piece of music that will be contemporary forever."[5]