The Pentecost Troparion: "Blessed art Thou, O Christ our God"

This beautiful chant is Georgian:  "K'urtkheul khar shen":


 
From the YouTube page:

Troparion of Pentecost, sung by the choir of the convent of Sameba-Jikheti. It can be found on their CD "Chant melodies."

"Blessed art Thou, O Christ our God, Who hast revealed the fishermen as most wise by sending down upon them the Holy Spirit - through them Thou didst draw the world into Thy net. O Lover of Man, glory to Thee!"

Here's a melody used by the Greek Orthodox Church for the same chant, sung in English:




And this is the same Troparion, sung to "Tone 8 / Russian Imperial Court Chant":




More about troparia here:

A troparion (Greek τροπάριον, plural: troparia, τροπάρια; Church Slavonic: тропа́рь, tropar′) in Byzantine music and in the religious music of Eastern Orthodox Christianity is a short hymn of one stanza, or one of a series of stanzas. The word probably derives from a diminutive of the Greek tropos (“something repeated”, “manner”, “fashion”). The early troparion was also called sticheron^{[citation needed]} (probably from stichos, “verse”); but currently the two terms are treated separately, with different melodies used for each.

Most troparia are chanted to one of the Eight Tones used in the Eastern liturgical tradition, though some have unique melodies to which they are chanted. Sometimes, troparia will be interpolated between verses of a psalm or other scripture.

In casual, unqualified use, troparion usually refers to the apolytikion (Greek: ἀπολυτίκιον), or "dismissal hymn", a troparion chanted near the end of Vespers which establishes the overall theme for the liturgical day, for which it is called the "troparion of the day". It is chanted again at the beginning of Matins, read at each of the Little Hours, and chanted at the Divine Liturgy following the Little Entrance.