sentences:  Since the Southern Slavic reception did not change the system the prosomoia, it corresponded to the Hagiopolitan Octoechos.Glas ("voice") 1–4 are the authentic modes or kyrioi echoi, and the remaining 5–8 are the plagal modes or plagioi echoi, the latter term coming from the Medieval Greek "plagios", "oblique" (from "plagos", "side").Unlike the Western octoechos, "glas" 5–8 (the plagioi echoi) used the same octave species like "glas" 1–4, but their final notes were a fifth lower on the bottom of the pentachord with respect to the finales of the kyrioi on the top of each pentachord, the melodic range composed in the plagioi was usually smaller.