The Hymn “0 Virgin Theotokos”, was composed by the Constantinopolitan Peter the “Sweet” (Bereketis or the Bereket in Turkish) in the 18th century and is chanted in vigils.
Peter composed the hymn in “Octoechos”, meaning he used all the eight modes of the Byzantine Music. The verse heared here chanted by Stanitsas, is the first one, in the 1st mode: “0 Virgin Theotokos”. The whole hymn:
“0 Virgin Theotokos,rejoice; Mary full of Grace, the Lord is with thee.
Blessed art thou among women and blessed is the fruit of thy womb.
For thou hast given birth to the Saviour of our souls”.

FROM:http://www.youtube.com/user/GreekOrthodox