(fl 1271). English theorist, active in Italy. He was a clerk and a member of the household of Cardinal Ottobono Fieschi (later Pope Adrian V), and wrote his Practica artis musice in the cardinal's house, perhaps in August 1271 at Viterbo where the cardinal was staying for the conclave. The work is explicitly designed for teaching practical music to boys and includes all the conventional notions of the period concerning musica plana. The central part of the work contains the tonary according to the practice of the French and English churches and the Roman curia. There is a chapter towards the end devoted to the composition of polyphonic music (cantilene organice); this chapter may be the first treatise on measured music written in Italy. The simple notes described are the long, brevis and semibrevis, in a binary relationship (i.e. the long equals two breves and four semibreves). Ligatures are equated to various rhythmic feet, and the greatest value is normally assigned to the last note.
P. Blanchard: Alfred le musicien et Alfred le philosophe, Rassegna gregoriana, viii (1909), 41932
J. Kromolicki: Die Practica artis musicae des Amerus und ihre Stellung in der Musiktheorie des Mittelalters (Berlin, 1909)
F.A. Gallo: La teoria della notazione in Italia dalla fine del XIII allinizio del XV secolo (Bologna, 1966), 13ff
M. Huglo: Les tonaires: inventaire, analyse, comparaison (Paris, 1971), 227ff, 3445
F.A. Gallo: Citazioni di teorici medievali nelle lettere di Giovanni del Lago, Quadrivium, xiv (1973), 17180
C. Ruini, ed.: Ameri Practica artis musice (1271), CSM, xxv (1977)
C. Ruini: Alcune osservazioni sulla Practica artis musice di Amerus, L'Ars Nova italiana del Trecento, v, ed. A. Ziino (Palermo, 1985), 21825
F. ALBERTO GALLO