(Lat.: ‘the going round’).
Literally the ‘course’ of a melodic line, but in the Middle Ages and later usually the range of scale degrees attributed to a given Mode, particularly in Gregorian chant, or the range of a voice, instrument or piece.
Writers from Marchetto (Lucidarium, ed. and trans. J.W. Herlinger, Chicago, 1985, bk ii, chap.2) to Tinctoris (Liber … tonorum, CSM, xi, chap.26) termed the modal ambitus perfect when it was a 9th or 10th, that is, the octave species plus one or two notes. From Gaffurius (Practica musicae, Milan, 1496/R, bk i, chap.8) onwards the perfect ambitus was usually equated to the octave species itself. The ambitus was called imperfect when it was less than the perfect ambitus, and pluperfect when it exceeded it. Tinctoris further refined this model to differentiate between the treatment of the upper and lower limit of the ambitus (Liber … tonorum, chaps.27–42). If a melody used notes from both an authentic mode and its plagal, the resultant mode of that melody was termed ‘mixtus’; if it used notes from the authentic or plagal versions of another mode, the mode was termed ‘commixtus’.
Synonyms for ‘ambitus’ used by medieval authors include ‘cursus’ (Johannes Cotto: De musica, CSM, i, chap.12), ‘processus’ and ‘medium’ (Jacques de Liège: Speculum musice, CSM, iii/6, 244 and 246). These were used by later theorists with the same meaning, for example ‘medium’ by Tinctoris (Liber … tonorum, chaps.1, 20) and ‘processo’ by Aaron (Trattato … di … tuoni di canto figurato, Venice, 1525/R, chaps.1, 4). The word ‘modulus’ is used for ‘ambitus’ in the Quaestiones in musica (ed. R. Steglich, Leipzig, 1911/R, p.45).
Ambitus is a significant aspect of musical style in Gregorian chant: in graduals and offertories, for example, the ambitus of the verse is usually higher than that of the respond. Stäblein (‘Zum Verständnis des “klassischen” Tropus’, AcM, xxxv, 1963, 84–95) noted that in troped introits the ambitus of the tropes differs from that of the introits.
HAROLD S. POWERS , RICHARD SHERR/FRANS WIERING