One can also consider the different functions that chant fulfils liturgically, and see how it may have developed over time to meet these in different ways, finally being consolidated into one body of practice.
Thus the prayers of the celebrant may have been intoned for the practical purposes of being heard more clearly over a longer distance, and also indicating to the Faithful where in the liturgy he was up to (consider the distinctive Sursum corda chant, which instantly indicates to the wandering mind where we are up to).
Then there are the ordinary prayers of the Mass: Kyrie, Gloria, Credo, Sanctus, Agnus Dei: these are natural opportunities for communal singing of penitence, adoration and so on, as they are the same words every week and can therefore have the same tune (or eventually, tunes). Communal singing has particular benefits, of course.
There are the proper prayers of the Mass, which change day by day: the Introit, Gradual, Tract, Alleluia verse, Offertory, and Communion. These are more likely to have been sung by a cantor or two, as they would be different every day.
There are also the prayers of the Office: above all the psalms, but also antiphons, and hymns; these would have been of particular importance in the monastic life, where the community would come together several times a day (and during the night) to sing. Given the need to sing the whole psalter (150 psalms) regularly, it is not surprising to find that simple melodic structures were developed which could be used to sing large numbers of psalms.
Each of these could have developed somewhat independently, and could have been influenced by other musical traditions from other cultures: certainly there are different styles associated with different elements of the Chant we have inherited.
Or it may not have happened that way. Perhaps the whole collection was dictated to Pope Gregory the Great by an angel.
But it is very important to understand that Chant is primarily an oral tradition: that is to say that it existed and was handed on from generation to generation long before it was written down.
Even when attempts were made to write it down, they are not fully understandable today.
But the breakthrough in handing on the music accurately came with the introduction of a staff to indicate pitch accurately.
This is attributed to a monk, Guido de Arrezzo, who wrote his theoretical work Micrologus around 1025.
From that time on, we are able to be fairly (but not absolutely) confident of the melodies of the chant. His four note stave, and the use of a clef (either Do or Fa) allow us to read the intervals between notes. The relationship between the notes is as in a modern major scale, with the only accidental being the possibility of flattening the Ti.
Chant notation only shows us relative, not absolute, pitch (as opposed to modern notation). The Cantor or Schola can pitch a piece wherever it suits them. And that is why I refer to notes by Do Re Mi, etc rather than C, D, E.
Interestingly, the terms Do, Re Mi, Fa, Sol, La (apart from Do, in fact) originate from this chant:
Ut queant laxis
Hymn for Second Vespers on the Feast of St John The Baptist, 24 June
So that these your servants can, with all their voice, to sing your wonderful feats, clean the blemish of our spotted lips. O Saint John!
This is the first verse of a hymn to St John the Baptist.
The first note of each phrase starts on each successive note of (what we would now call) a major scale, and the corresponding syllables are Ut Re Mi Fa Sol La. Ut is still used in continental Europe, though in English we have replaced it with Do (from the first syllable of Domine, I have been told, but cannot verify that).
Note that this piece is written with a Fa clef, and the syllable Fa does indeed fall on the line indicated by the clef.
In the next post in this series, I will address the issue of notation in a little more detail, particularly with regard to the rather more contested issue of rhythm. Then I shall go on to look at different types of chant, with lots of links both to notation and recording to illustrate what I am trying to convey.