It has become increasingly difficult to categorize modern jazz. A large segment of the music does not fit into any historical style; it is not as rock-oriented as fusion or as free as avant garde. Starting with the rise of Wynton Marsalis in 1979, a whole generation of younger players chose to play an updated variety of hard bop that was also influenced by the mid-'60s' Miles Davis Quintet and aspects of free jazz. Since this music (which often features complex chordal improvisation) has become the norm for jazz in the 1990s, the terms modern mainstream or Post-Bop are used for everything from Wallace Roney to John Scofield, and symbolize the eclectic scene as jazz enters its second century. -- Scott Yanow