This hymn is beyond beautiful. Attributed to the Eastern Christians of the 2nd Century, from eh same time period we received the Kyrie Eleision from the west, this hymn is a paramount blessing and triune praise. Sang here in English and followed by the Greek, https://www.youtube.com/watch?v=oJ6of7ViJ5w I would love to see this and other songs brought into Orthodox Reformed Protestant worship. I am a high churchman (as much as you can be within the Dutch tradition). What do you know about this song? Are there others you could suggest?
Being formerly EO, I have heard it countless times. Much like the Latin at the end of the Gloria (Sanctus, Dominus, Altissimus), the Greek (Theos, Ischyros, Athanatos) and the English (God, Mighty, Immortal) proceeds with each part having one more syllable than its predecessor, to help provide a crescendo effect. It is also an option at the beginning of the Rite II Eucharist at the beginning of the 1979 BCP, though I have never seen it used. In EO daily domestic prayers it is typically prayed once or twice in the morning and once or twice again in the evening.