Prescience in Their Language - Two Composers

It's one issue that we all recognize; that is, the overwhelming power of genius represented by the likes of a few children, such as a Mozart, or a Mendelssohn. The supreme glibness of their production defies description.
It's another issue, perhaps, to consider examples of personal language that are immediately identifiable or recognized in the Romantic aspect, and which are brought to us by teen-agers whose thematic utterances are so unique as to remain, in essence, theirs and only theirs throughout their lives from their very beginnings.
I think often of Chopin and Rachmaninoff in this particular arena of thought.
We are told that Chopin wrote his first piano concerto in 1830; actually, some of the thematic material and workings of this composition were created at age 17. That first wonderful theme was given us during that tender age, and it is redolent with an eclecticism that belies such a tender age.
The same applies to the first concerto by Rachmaninoff, who began conception of that work at age 17 as well, even though we know that he altered the work later in his career. The first theme in his concerto, as in the Chopin, remains as it has always been, and it is very clear to the listener who these composers are, in terms of the uniqueness of their thematic projections. They, from the very beginning are , and remain, Chopin and Rachmaninoff.