Hymne à Saint Jean-Baptiste
Ut Queant Laxis . . .
Attributed to Guido d'Arrezzo, (circa 991 - 1033)
The Choir of Amiens Cathedral (France) showing the high altar and choir with
In much of the 18th and 19th centuries, the Serpent, a deep voiced hybrid wind instrument, was sometimes used to support choral singing, as evidenced in the above painting by the English painter Charles Wild (1781–1835).
This four part harmony arrangement by Anthony M Alcock has a foundation provided by a double bass, (there not being many such serpents alive anymore).
Here, the singing voices are synthetically produced by the Sibelius music editing system, consequently there is no latin text, just a lot of " A-ahs ".
"Ut queant laxis" or "Hymnus in Ioannem" is a Latin hymn in honour of John the Baptist, and traditionally attributed to Paulus Diaconus, the eighth century Lombard historian. It is famous for its part in the history of musical notation; the hymn belongs to the tradition of Gregorian chant.
This chant is useful for teaching singing because of the way it uses successive notes of the scale: the first six musical phrases of each stanza begin on a successively higher notes of the hexachord, giving ut–re–mi–fa–so–la; though ut is replaced by do in modern solfège. The naming of the notes of the hexachord by the first syllable of each hemistich (half line of verse) of the first verse is usually attributed to Guido of Arezzo. Guido, who was active in the eleventh century, is regarded as the father of modern musical notation.
The first stanza is:
Ut queant laxīs
It may be translated:
So that your servants may,
with loosened voices,
resound the wonders of your deeds,
clean the guilt from our stained lips,
O Saint John.
Most of the above information is drawn from Wikipedia.