Example 21. O canenda/Rex quem/REX REGUM/[CONTRATENOR], breves 1–14 (in modern values, where a medieval breve is transcribed as a modern dotted breve). Arrows above the system mark the modus onset of the triplum, motetus, and tenor; the contratenor modus onsets are marked by arrows above its stave. The sonority classification for each breve is noted below the system. The dashed boxes mark the moment when the onset of modus coincides in all four voices