DIAFONIA. – A genre of composition in early polyphony (v. ARS ANTIQUA), whose name was used by medieval theorists (9th–12th centuries) as equivalent to organum, indicating a technique in which parallel motion still predominates, whereas in discant contrary motion would prevail.
Rules for d. are found especially in chap. 13 of the Musica enchiriadis, from the 10th century (v. Gerbert, Scriptores ecclesiastici de musica sacra potissimum, St-Blasien 1784, I, pp. 165–166), and in chaps. 18 and 19 of Guido d’Arezzo’s Micrologus (ibid., II, chaps. 18, 19, pp. 21–23). The first treatise prescribes the intervals of the 4th, 5th, and octave, whereas the second proposes those of the major 2nd, major and minor 3rds, and 4th. Luisa Cervelli