I'm currently reading Don Quixote, and the lyrics of his songs don't rhyme at all, but that's understandable since it was translated from Spanish, but it made start thinking about how older books sometimes have song lyrics, and that those songs usually don't rhyme (and there also always seems to be a tale involved in the lyrics).
The other best example to go with my question (off the top of my head), is Piers Plowman, which, written anywhere between 1130 and 1400, features songs that, if described as poetry instead of music, would be believable to me. The words don't rhyme, and it appears to tell a story.
So, again, my question is, what was the method of writing songs back in the middle ages and then into the Renaissance era? Was it just to tell a story, or are there more complexities that my dim mind is missing. I've tried looking for answers online but can't seem to garner any articles other than click bait when it comes to older styles of songwriting.
Older lyric poems and ballads, songs, and epic poems to be performed orally, etc., were usually composed with one of two things in mind (though sometimes both), and those are meter and rhyme scheme.
If we look at the Homeric epics of the Iliad and the Odyssey, then we’ll see they were written in dactylic hexameter, meaning each line of poetry is broken up into six ‘feet’ and each foot consisting of short and long syllables. In the case of Ancient Greek and Latin epic poetry (which, again, was meant to be recited orally, perhaps with music), these dactyls (‘feet’) with their short and long syllables create the rhythm and musicality.
Later in, let’s say, medieval Italian poetry, there are specific rhyme schemes in works that could have been accompanied by music. Some notable examples include the ABBA ABBA CDC CDC (or ABBA ABBA CDE CDE, etc.) pattern found in a number of Italian sonnets. Other works, though perhaps not meant to be performed, were written in both hendecasyllabic meter (i.e., eleven syllables per line) and a rhyme scheme, such as the famous Commedia of Dante Alighieri —the rhyme scheme (terza rima) follows an ABA BCB CDC DED, etc. pattern.
TL;DR: It will depend on time, place, and author, but older lyrics, poems, ballads, and other lyrical works to be performed with music followed meter, a specific rhyme scheme in the original language, or both.