The success of the motet in the 13th century was striking, but it was not exclusive. Another form was being practised concurrently: the polyphonic conductus,both more unitary in the modern sense of the term and more immediately comprehensible. The fundamental difference between the motet and the conductuswas that, unlike the former which was built on a pre-existing plainsong tenor,the conductusused a composed cantus firmus;it was thus an entirely original work although the actual process of its composition was not new. The procedure was still one of a successive accumulation of counterpoints above a foundation voice. This was written for the occasion and although comparable to the tenorof a motet, it had a livelier popular rhythm and was greater in length so that it did not have to be repeated, as in the motet. Being therefore less abstract than the tenorof the motet, this voice was less alien to polyphony, which was to model its proceedings after it. Whereas in the motet the time values of the notes diminished as they ascended from the duplumto the triplumand quadruplum,the conductushad the same rhythm in all the voices and also the same text. Originally the conductuswas a monodic processional song intended to accompany the actions of the priest or the faithful during the service -- hence its name. But by the end of the 12th century it had been affected by the advent of polyphony. Although he wrote conductus for one voice, as in the Beata viscera,Pérotin also produced examples for two voices and for three voices, the latter in the very beautiful Salvatoris hodieintended for the feast of the Circumcision. Like the motet, the conductusfailed to find a place in the liturgy. After having provided a whole collection of pious but extraliturgic pieces, it became increasingly profane while retaining the use of the Latin language. A good example of this secularization is the anonymous conductus,Veris ad imperiawhich, with its refrain Eiaand its spontaneous character of a popular dance, is a wonderful evocation of the awakening of nature at Spring's behest. All in all, the conductuswas the Latin equivalent of the works of troubadours and trouvères and it may be this that explains its decline into total disuse in the first quarter of the 13th century. While the 'church' composers preferred the elaborations of the motet form, the troubadours and their successors evolved the polyphonic rondeau.