A very interesting note about this specific chant is that while it is one text and chanted as a whole, it contains all 8 tones of Byzantine Music. Each phrase is chanted in one of those 8 tones. The first two phrases are the glorification of the Trinity (hence the type of the chant as a Doxastikon - ie a glorification hymn). This fantastic piece is chanted at Vespers of the Feast of the Dormition of the Virgin Mary, i.e. 15th August.