I have little doubt you are all fascinated by the history of lyrics of Christian hymnody. Sure you are, I can hear it in your silvery voices. Nothing would make you happier than Part One: Ancient Hymnody.
The early church did not make the sharp division between songs, prayers, and readings that we, especially in the Protestant churches, do today. Those used to a liturgical service know the distinction. There are set musical pieces that occur throughout the worship, to which the lyrics are not optional or very limited in choice. Most of these lyrics come straight from the scriptures without alteration.
Holy, Holy, Holy Lord, God of power and might. Heaven and earth are full of your glory...
Christ became obedient unto death, even death on a cross...
Any inserted special music would be recitation of psalms. Whatever creative energy a person might have went into the music. In modern liturgical services there will often be hymns with composed lyrics, but this doesn't seem to be the case in the early church. It is ironic that the churches which advertise themselves as "biblical" often have hymns only drawn from the scriptures at some distance; the liturgical churches they disapprove of have great raw hunks of scripture, too big to swallow at one sitting.
In examining a lyric, I use a few obvious question: who are the words addressing? Is the presumed hearer the congregation, God, or the world at large? What is the theological focus? Is it a work of exaltation, of evangelism, of storytelling?
In the early church, this division is less sharp than we are used to now. When we say Christ, O lamb of God, who takes away the sins of the world... it is pretty clear that we are speaking directly to Jesus. But what about This is the feast of victory for our God... or Christ has died, Christ is risen, Christ will come again. It is hard to tell exactly, and quite unimportant, whether these declarations are evangelistic, teaching, or praise.
These are the lyrics handed down since earliest days. Declarative, communal, straight from scripture. But there is a hint in the Epistles of something else happening. "Speak to one another with psalms, hymns and spiritual songs." Ephesians 5:19. Spiritual songs...what are those, exactly? There is some sense in this. Even in a far more formal and liturgical culture than ours, do we imagine that folks encouraged each other by launching into a Kyrie? Hardly. There may not have been a Syriac "Arky, Arky," but they must have sung something other than the liturgy to send babies to sleep.
From the 7th Century:
Christus Factus Est Pro Nobis
Christus Factus Est Pro Nobis Christ became for us
Obediens usque ad mortem Obedient unto death
Mortem autem crucis Even to the death of the cross
Propter quod et Deus exaltavit illum For which cause God hath also exalted him
Et dedit illi nomen And hath given him a name
Quod est super omne nomen. Which is above all names
Update: In response to Jerub-baal's comment, I share the poor results of my research. There is an online radio station which plays Gregorian chant, and there are sites devoted to the Syriac, Melkite, and Coptic traditions. There are also two which cover the Orthodox tradition fairly thoroughly. There is also Ambrosian Chant, which I know nothing about, but ran across references to.