Te Deum 5th century

This is a 5th century early monastic chant.  The version I found began with church bells that immediately gave it an authentic tone.  After the singing began, the bells continued in the background which gave the whole song a very peaceful feeling.  The quality of the recording also made it seem as if it was sung in a large room with great acoustics.  It was not hard to picture monks in a beautiful monastery prayerfully singing.

This is the recording that I listened to.
youtube recording

I was able to find the notation and the text in the liber useralis.
liber useralis

This confirmed my original impression that it was in Phrygian mode, or mode 3.  After seeing the notation, it also confirmed that it was neumatic with mostly one syllable per note except for a few exceptions.  It was performed in a responsorial fashion with one man singing phrases and a chorus repeating the phrases.

The tone of the entire piece was solemn and prayerful.  I learned through my research that this was a hymn of thanksgiving and joy.  The solemn tone is not what I normally associate with hymns of joy and thanksgiving in our modern day.  I usually think of joy and thanksgiving being expressed in a more jubilant way, with a faster tempo and more variety and expression, but I understand that joy and thanksgiving can be expressed in a solemn and prayerful way as well.

I learned from my research that this hymn was originally attributed to St. Ambrose or St. Augustine, but is now accredited to Nicetas, Bishop of Remesiana (4th century). " It is used at the conclusion of the Office of the Readings for the Liturgy of the Hours on Sundays outside Lent, daily during the Octaves of Christmas and Easter, and on Solemnities and Feast Days. The petitions at the end were added at a later time and are optional. A partial indulgence is granted to the faithful who recite it in thanksgiving and a plenary indulgence is granted if the hymn is recited publicly on the last day of the year." source

I was able to read the English translation which is about 8 paragraphs long.  It gave praise to the Father, the son and the Holy Spirit,and included a lot of other doctrine/theology mentioning the virgin birth, the death of Christ, and his position at the right hand of the Father.  The end which according to the paragraph above was added later and includes several petitions.