Spiritual songs > Hymns to the Mother of God
Rejoice, O Virgin Theotokos
This is actually a troparia to the Mother of God, which is sung at the end of Vespers before the blessing of bread for major feasts. But since the text is well-kmown (as the Byzantine version of the "Hail Mary"), it is often sung before or after services, or as a general Marian anthem. For the Slavonic version, see Bohorodice D'ivo.
Sources
Text and music were included in the "Liturgical and Scriptural Hymns" section of The Divine Liturgies of our holy fathers John Chrysostom and Basil the Great (2005), our green Divine Liturgies book, on page 453.
And earlier English translation, with music, was included in the Marian Hymnal (1984) on page 19, under the title, O Godbearer Virgin:
O Godbearer Virgin Mother now rejoice!
Holy Mary full of grace, the Lord is with you.
Blessed are you among women and blessed is the fruit of your womb,
for you have borne Christ the Savior,
the Deliverer of our souls.
The primary difference here is the change from Godbearer (which strictly speaking is Theophoros, God-carrier, a title given to certain monastic and apostolic saints) to Theotokos, "she who have birth to God."