I can't think of two styles of music more diametrically polar opposites than jazz and freeform.
Opera is always based on classical modes (major or minor), every note is written out, and the rhythm is generally a straight-ahead 4|4 or 3|4 with no syncopation or swing. The emphasis is almost always on the vocalist who is given no freedom to experiment. The vocal charts often contain scales and intervals that resemble more of a strict vocal excercise rather than picking notes for their expressive or emotive value. The communication is in the lyrics more so than in the music.
Jazz is 90+percent improvization by vocalists and players alike, they use all kinds of modalities from blues scales to modes common to foreign styles of music. It is often up-tempo and usually has a syncopated "swing" component to the rhythm, meters include unusual combinations such a 5|4 or 7|8. The choice of notes is about feeling and expression in the performance, as if the instruments are talking to you.
In all honesty, I used to like jazz more than I do now. I was a big fan of Miles Davis and the 60s and 70s style. The new smooth jazz is not exactly my thing, though I "get it."