The only constant in the music of Muhal Richard Abrams is change. He composes complex scores full of mobile colors, textures, instrument groupings, and melodies that sometimes clash and sometimes complement. On the other hand, his familiar “Blues Forever” is a straightforward big-band swinger that’ll knock your socks off. As a pianist he ranges from lush impressionism to long lines of barbed-wire dissonance. He thrives on free jazz and third-stream music, even as moments of gospel, blues, bop, and ragtime sneak into his performances. For half of his Ravinia concert he’ll play with his New York octet; for the other half he’ll lead an extra-special unit: four former students and colleagues from the 1960s, when Abrams lived in Chicago and was the guiding spirit of the then-young Association for the Advancement of Creative musicians. The four are woodwind men Anthony Braxton and Roscoe Mitchell, bassist Malachi Favors Maghostut, and drummer Thurman Barker, all of whom have long been opening the frontiers of free jazz–and probably none of whom would have become major jazz artists without Abrams’s inspiration. The Jazz Institute of Chicago and the Lila Wallace/Reader’s Digest National Jazz Network are sponsoring Abrams’s Chicago visit, which will include a lecture-demonstration on the 27th and a workshop on the 29th on large- and small-group composition techniques (both events are free to the public; call 427-1676). Thursday, 7:30 PM, Bennett Hall, Ravinia Festival, Green Bay and Lake Cook Rds., Highland Park; 728-4642.