St. Cosmas, surnamed the Melodist, was foster-brother of John of Damascus, to whom he was attached by closest bonds of friendship. He retired with the famous theologian and hymn writer, to the monastery of St. Sabas, in Palestine, where he spent his leisure in the composition of hymns, many of which found their way, along with those of John of Damascus, into the Greek Offices. There he also shared the work connected with the preparation of The Octoechus with his foster-brother. To what extent his hymns found a place in the Greek Offices, it is difficult to say. If all those bearing his name are accepted as his, then his contribution is a fairly large one. He is represented by canons on The Nativity, The Epiphany, The Transfiguration, and Palm Sunday; also by sundry other pieces. His poetry, although it is said they composed in friendly rivalry, cannot bear comparison with that of St. John, in any particular. It has, however, qualities which claim for it the appreciative reference which Dr. Neale bestows upon it.
Cosmas became Bishop of Maiuma, near Gaza, in 743, and died about 760. He is commemorated by the Greek Church on October 14th.