For half a millennium ecclesiastical polyphony retained the hovering timelessness of the chant from which it had sprung. Then, after 1400, it began to change. The harmony became simpler, fuller, and stronger, in the process developing the powerful organizing force, radiating out from cadences of an entirely new type, that we call 'tonality'. The power depended upon the simplicity, and both came largely from popular music.
An example of late medieval music just touched by tonality in this sense is 'Adieu m'amour', by the northern French composer Binchois (Ex. 6.1). It is for a solo voice, the cantus, accompanied by two counterpoints, the tenor and contratenor, the former (so called because it originally 'held' the main tune) maintaining its own smooth melody while the latter rather awkwardly fills out the harmony. Each of the principal two voices has its own distinct form of cadence: ii(\♭)→i in the case of the tenor, and vi(♭)→i+ (the 'Landini'1 or 'under-third' cadence) in that of the cantus. These always occur together, so that their polyphonic relationship is fixed (vi/ii→i+/i or vi♭/ ii ♭→+/ i); but not,be it noticed, their position within the mode. Already we see the beginnings of a hierarchic key system. It is worth noticing, too, that these proto-keys conform to the pentatonic seventh (C, G, E, A), and that the under-third cadences greatly strengthen this pentatonic impression.
Against these cadences in the cantus and tenor, the contratenor executes two distinct progressions: iv(♯)→v, when the 'key' is G, E, or A (as in the bracketed Cadences 1,4, 5, and 6), but v –→v when it is C (Cadences 2,3, and 7). The first of these progressions gives one of the medieval cadences ('Lydian' or 'Phrygian',2 depending on the context); the second, a makeshift version of the full close. This cadence, with its queer-looking octave leap, remained in common use for the rest
1 So called after the Florentine composer Francesco Landini (c. 1325–97), who, though not actually the
inventor of this cadence, made much use of it. Strictly speaking, the Landini cadence is a particular type of
under-third cadence with the contour (i+–vii(♭)–vi(♭)→i+, elaborated by Binchois into i+–vii(\♭)–i+–vi(♯x266D;)→i+).
2 So called because of the 'Lydian ' iv(♯) and 'Phrygian' ii(♭); otherwise, these cadences have no necessary
connection with the modes they are named after.