613: Africa. Shona Mbira Music Recorded in Rhodesia 615: Conlon Nancarrow, Study No. 40 for Player Piano (1973–74?) 617: Conlon Nancarrow, letter to György Ligeti, 30 June 1982 619: György Ligeti, Études pour piano, Livre 1 (1985), early verbal sketch 620: György Ligeti, Études pour piano, Livre 1 (1985) 624: György Ligeti, Études pour piano, Livre 1 (1985)