Sequentia cyclica

Kaikhosru Shapurji Sorabji, the piece's composer, around 1950

Sequentia cyclica super "Dies irae" ex Missa pro defunctis, commonly known as Sequentia cyclica, is a piano composition by Kaikhosru Shapurji Sorabji. Written between 1948 and 1949, it is a set of 27 variations on the medieval sequence Dies irae and is widely considered one of Sorabji's greatest works. With a duration of about eight hours, it is one of the longest piano pieces of all time.