This is a hymn in Old Church Slavonic, not in Church Slavonic that you'll probably hear in an Orthodox Church. OCS is an older form of Slavonic and is not used in any church today. There are only such experimental projects like this hymn, or the Old Church Slavonic Wikipedia: http://cu.wikipedia.org
The hymn is from a manuscript containing texts used during holy mass, written in the Glagolitic alphabet. The language is of the Great Moravian dialect, ancestor of modern Slovak and Moravian. It is also the oldest Old Church Slavonic manuscript known today!http://www.youtube.com/watch?v=tJJGu7fK ... re=related
Text in Cyrillic:
Цѣсарьствѣ нашємъ господі, мілостьѭ твоєѭ прізьрі: і нє отъдазь нашєго тѹзімъ, і нє обраті насъ въ плѣнъ народомъ поганьскъимъ: Хріста раді господі нашєго, іжє цѣсарітъ съ отьцємь і съ Свѩтъимь Дѹхомь.
In Glagolitic:http://titus.uni-frankfurt.de/texte/etc ... evf004.htm
(Folia 4, Page b, starts at Line 7.)http://en.wikipedia.org/wiki/Kiev_Missal