In the 13th century, composer Petrus de Cruce developed a unique style of motet that exaggerated the stratification of rhythmic levels. In “Petronian” motets, the top voice (triplum) is incredibly fleet; the middle voice (motetus) uses rhythms of intermediate duration; and the low voice (tenor) plods along in longs (dotted half notes). This effect was made to be heard – the listener can clearly discern the layering of rhythmical levels according to range.
Also note the text(s): as mentioned in the previous post, polytextuality is a defining (and definingly odd) characteristic of the motet. “Aucun ont trouvé” is composed of two love poems in French. The first poem (in the triplum) is considerably longer, as that voice functions at a higher rhythmic level. And underpinning it all is the tenor, which annunciates only one single word.
The Taruskin Challenge 