Oktōēchos (here transcribed "Octoechos"; Greek: ὁ Ὀκτώηχος pronounced in koine: Greek pronunciation: [okˈtóixos]; from ὀκτώ "eight" and ἦχος "sound, mode" called echos; Slavonic: Осмогласие, Osmoglasie from о́смь "eight" and гласъ "voice, sound") is the name of the eight mode system used for the composition of religious chant in most Christian churches during the Middle Ages. In a modified form the octoechos is still regarded as the foundation of the tradition of monodic Orthodox chant today (Neobyzantine Octoechos).