Ever since the first systematic study of Peruvian music (d'Harcourts 1925), musicologists have puzzled over the relationship of pentatonic, or five-note music, to other modes of music in the Andes. At that time the enquiry was related to the general musicological debate over whether the pentatonic was the universal form of primitive ‘scale’, from which all other musical scales have evolved. This debate was enmeshed with the hypothesis of nineteenth-century anthropology, that this most basic form of musical system could be derived from a human physiological capacity to distinguish the consonances of the intervals of the fourth, the fifth and the octave. Within this evolutionary paradigm, the accumulation of examples of pentatonic melody from the Peruvian Andes was easily interpreted as further evidence of the universality of this form among primitive people.