Opus Clavicembalisticum

Opus clavicembalisticum is a solo piano piece composed by Kaikhosru Shapurji Sorabji, completed on June 26, 1930.

The piece is notable for its length and difficulty: at the time of its completion it was the longest piano piece in existence. Its duration is around four hours, depending on tempo. Several of Sorabji's later works, such as the Symphonic Variations for Piano (which occupy 484 A3 pages of manuscript—probably about nine hours of music, similar in duration to Frederic Rzewski's work The Road) are even longer.

At the date of conception, the piece was possibly the most technically demanding solo piano work in existence due, for the most part, to its extreme length and arrhythmic nature, although later works by New Complexity, modernist and avant-garde composers, along with Sorabji himself, conceived more difficult pieces; it is in this particular area that Opus clavicembalisticum primarily receives its notoriety, and to this day is still highly regarded in this light.

Sorabji may have been inspired to compose the work after hearing a performance of Busoni's Fantasia contrappuntistica by Egon Petri, and Opus clavicembalisticum is an homage to Busoni's work.