This is a study on the microtonal aspects of György Ligeti's Hamburgisches Konzert (Horn Concerto), with special reference to its relationship with the American composer Harry Partch, but also with Gérard Grisey and Claude Vivier. The special mixture of equal temperament versus just intonation is analyzed. The movement "Choral" is confronted with Harry Partch's idea of "tonality flux". The work is shown with its inherent long chain of exploratory forms of thought in Ligeti's compositional work as to microtonality. The Viola Solo Sonata (1991-94) contains in the first movement "Hora lunga" a sign world new to Ligeti for natural intervals. He adopts these signs for the Hamburgisches Konzert. In an appendix, Ligeti himself is presented with several of his ideas about Partch, Vivier and microtonality on the whole, in an interview and in several of his writings.
