An old friend of mine is a poet. He points out that up until recent times, almost all the literature that we know about (e.g., Homer, other Greek and Roman works, especially drama, Psalms, Icelandic Sagas, Beowulf, Shakespeare and other playwrights, etc.) is in poetic form, as opposed to prose. Books and scrolls were expensive, rare (had to be hand-copied, remember), and cumbersome to carry about. Concurrently, only a small portion of the population was able to read. Skalds, bards, troubadours, and minstrels were the main forms of transmission.   They performed these works, not reading them, but reciting them from memory, usually chanting them or singing them to the accompaniment of lyre, harp, or similar instrument.

My friend's theory (which he says is not just his theory) is that rhyme and meter are mnemonic devices. It's a heck of a lot easier to memorize something that has a standard verse form (e.g. four lines of iambic pentameter with an end-rhyme scheme of aabb, followed by two lines of repetitive refrain with the same meter and rhyme scheme). A good strophic (repeating) melody is a further—and very powerful—mnemonic device. All aids to memorization.

A paragraph or two of prose is a heck of a lot harder to memorize, as are some singer-songwriter products that tend toward the amorphous, as so many of them do. A songwriter has to be, first of all, a competent poet. If a song you've written doesn't contain a fairly universal concept that catches the imagination, and if it doesn't follow a consistent enough form to make it easy to memorize, and if it doesn't have a melody that lingers in the mind, it's doubtful that anybody else will learn it and sing it. No future folk song there.

Don Firth