Though the use of the rhythmic modes is the most characteristic feature of the music of the late Notre Dame school, especially the compositions of Pérotin, they are also predominant in much of the rest of the music of the "ars antiqua" until about the middle of the 13th century. Composition types which were permeated by the modal rhythm include Notre Dame organum (most famously, the organum triplum and organum quadruplum of Pérotin), conductus, and discant clausulae. Later in the century, the motets by Petrus de Cruce and the many anonymous composers, which were descended from discant clausulae, also used modal rhythm, often with much greater complexity than was found earlier in the century: for example each voice sometimes sang in a different mode, as well as a different language.