Probably a 15th Century French church hymn, this a deep and wonderful Christmas carol. Arranged as a Greek bouzouki instrumental.
In the improvisation part I use several Balkan-style scales, one of which is the Minor Pentatonic. This is done purposely: the North-West of Greece is the cradle of the Ikariotiki music. Large part of that music is being delivered in the Pentatonic, one of the most ancient Modes.