From 1985 to 2001, Ligeti completed three books of Études for piano (Book I, 1985; Book II, 1988–94; Book III, 1995–2001). Comprising eighteen compositions in all, the Études draw from a diverse range of sources, including gamelan, African polyrhythms, Béla Bartók, Conlon Nancarrow, Thelonious Monk, and Bill Evans. Book I was written as preparation for the Piano Concerto, which contains a number of similar motivic and melodic elements. Ligeti’s music from the last two decades of his life is unmistakable for its rhythmic complexity. Writing about his first book of Piano Études, the composer claims this rhythmic complexity stems from two vastly different sources of inspiration: the Romantic-era piano music of Chopin and Schumann and the indigenous music of sub-Saharan Africa.