What is rock-jazz?

Answer 1

The attempted fusion of the two genres initiated by jazz musicians in an attempt cash into the much larger market for rock music than for jazz, sometimes successfully achieved and more often a dismal failure. Nevertheless, a few iconic recordings came about because of it, namely Herbie Hancock's "Head Hunters" and some of the earlier recordings by Joe Zawinul's seminal jazz/rock band, "Weather Report". Of course, there were many more successful recordings as well as the best forgotten. Today, jazz/rock fusion is mainly an historical footnote in the history of Jazz Music though it still pops up its head from time to time.

Answer 2

For anyone who is music terminology literate, the biggest technical difference is syncopation. Jazz music is syncopated (swung eighth notes) while rock is more defined as having eighth notes played straight. However, music is not black and white, and it should be known most rock comes from jazz.