Before I go into progressive detail, a few introductory comments to this subject.
I have stated as axiomatic that language is the mother of all other (symbolic) systems, and affirmed the necessity of keeping this in mind at all times.
In order to talk about the physical world, to talk ABOUT anything, we have recourse to language. So... any theory MUST take into account the manner in which we are expressing it, and must take into account the nature of language itself.
Some basic observations : speech and writing, while both language, are NOT the same thing at all. Writing is the translation of speech into a separate but related symbolic system which has different properties from speech. (Speech is ephemeral, it is sound, apprehended by the ears.)
Now, what's the relation to Sappho ?
I have in front of me a best selling album by Angélique Ionatos, a French-Greek artist who set some of Sappho's poetry to her own music.
Some general culture : Sappho was a little slip of a woman poet living some 2500 years ago on the Greek islands. We don't know a hell of a lot about her, (and I will dismiss the trite assumption that she was homosexual ; ancient Greek sexuality was light years away from our own...) ; she was probably not even very pretty, but a few of her poems, and many fragments have come down to us through the ages. Because she was a poet, a writer, and she knew just what she was trying to do, and what it was worth. And posterity respected her for it, and gave her credit where it was due.
Here she is :
I write my verses on air
And they love them
I have served beauty
Was there anything greater for me ?
Even in the future, I say, they will remember me.
Little cheater, little liar, Sappho, and she knows it. Poetry is air, it is speech, it is an acoustic image, but, in order for her work to descend through the ages, it had to be written down.
If speech is ephemeral, (just like our bodies, promised to death and decay...) then the written word is immortal.
But poetry, that's having your cake and eating it too. It's ephemeral and immortal.
I'll give two other examples before digging into the technical, dry stuff...
On the album, Ionatos recites one poem in the original ancient Greek. It is awesome to imagine that this has traversed more than 2 millenia to reach us, and that we can STILL be moved by it...