thallo wrote:responses were added in the meantime :-)
We must pay close attention to the dates until the very end. Jazz is not a constant thing; there have been styles, evolutions, and influences. When I have time, I go looking for Russian things from the late '800s, because in my opinion we can find interesting ones well before jazz arrived.
Without overthinking it, one can talk about ragtime, but I am curious to hear those pieces. It is a precursor to jazz and syncopated time. In fact, the bass generally has homorhythmic figures while the melody is written with accents shifted relative to the classical conception of rhythm.
So, speaking more simply of a ragtime piano piece in 2/4, we have:
homorhythmic left hand (usually eighths or quarters played on the strong accents) + right hand with syncopated rhythm = polyrhythm.
Now I don't know if I am saying something obvious, regardless of the polyrhythm, but I was never taught any other type of approach besides the classical one. This opened me up and explained better to me what rhythm is.
Let's take a simple triplet as an example: to me, and I think to almost everyone, they taught us to say one-two-three, in order to understand the rhythm and be able to solfège it.
Then, instead, after starting to associate words or syllables that are musical, the rhythmic sequence has a different and more musical meaning: the rhythm therefore assumes a behavioral attitude, in addition to a mathematical division.
For example, in India, they teach ta-ca-ti instead of one-two-three.
A book I recommend where I learned this concept is
How To Sight Read Jazz and Syncopated Type Rhythms - Mike Longo
So, for every rhythmic figure, instead of saying the usual thing, a succession of syllables is associated, which varies from individual to individual, in order to identify each rhythmic figure. From the syncopation to the quintuplet.
P.s. I hope I haven't written too much nonsense, and on the contrary, I urge you to correct or integrate what I have written.