In 1965, four individualistic and visionary Chicago jazzmen established the Association for the Advancement of Creative Musicians; in 1990, for the organization’s 25th anniversary, three of those four mandarins–pianists Muhal Richard Abrams and Jodie Christian and trumpeter Phil Cohran–will be put to work. (The other founder, drummer Steve McCall, died in 1989.) Of course, there were many others who played important roles in the A.A.C.M.’s early years–particularly Anthony Braxton and the members of the Art Ensemble of Chicago, who sojourned in Europe and spurred the jazz world to refocus its attention on events in the midwest–but if you’re gonna start a historic celebration, it might as well be at the beginning. joining the founders will be a couple other longtime contributors–bassist Malachi Favors Maghostut and drummer Ajaramu–and reedman Gene Easton. Tonight, 8 PM, Getz Theater, 72 E. 11th; 445-8356. (Amina Claudine Myers and Shadow Vignettes, the big band led by Edward Wilkerson, will also appear on this program, which kicks off the weekend-long anniversary festival. Concerts continue through Sunday; other activities include midnight jam sessions at the Southend Musicworks and a Saturday-afternoon panel discussion at Columbia College on the A.A.C.M.’s place in 20th-century music.)