
1) Ancient Greek music 2) Byzantine music 3) Byzantine Rite
Found on
https://www.crosswordclues.com/clue/octoechos

Oktōēchos (here transcribed `Octoechos`; Greek: ὁ Ὀκτώηχος okˈtóixos; from ὀκτώ `eight` and ἦχος `sound, mode` called echos; Slavonic: Осмогласие, Osmoglasie from о́смь `eight` and гласъ, Glagolitic: ⰳⰾⰰⱄⱏ, `voice, sound`) is the name of the eight-mode system used for the composition...
Found on
http://en.wikipedia.org/wiki/Octoechos
[liturgy] The liturgical book called Octoechos (here transcribed `Octoechos`; Greek: ἡ Ὀκτώηχος okˈtoixos; from ὀκτώ `eight` and ἦχος `sound, mode` called echos; Slavonic: Осмѡгласникъ, Osmoglasnik from о́смь `eight` and гласъ `voice, sound`) contains a repertoire of hymns ordered in eight parts a...
Found on
http://en.wikipedia.org/wiki/Octoechos_(liturgy)
No exact match found.