I'm not sure how close this is to your topic, but composers, like Beethoven, Bach, Mozart used to do "variations" on a theme written by other composers who were at or around their same technical level.

I enjoy taking (for example)a Country tune by Hank Williams or one of his contemporaries, and doing jazz style chord substitutions, maybe playing the first of the tune "straight" and then "subbing in" the last verse and/or chorus. I used to it quite often when I played in the restaurant venue, and it was nice when someone caught on to my little flights away from the norm.

I had a fairly good grounding in classical piano and could sight-read very well, but I really did not learn how to "play" until I developed a better ear (and therefore, better musical "sense") and could actually improvise on a standard classical piece.

Having this skill, albeit basic at the the time, and then being able to develop it further by playing with musicians far more experienced than I, really opened my ears to the joys of improvisation and re-harmonization in genres of music other than classical.

Another player, although not actually a bona fide "jazzer" who returned to classical form was Billy Joel.

Good luck with your perfornmances, Russ...I'm a Michel Legrand fan from way back...I enjoy playing around with "Windmills of Your Mind" and "What are You Doing the Rest of Your Life?".

I still like to play around with the classics, and have developed several accompaniment styles on my Tyros4 for just those occasions.

Ian