When he's taking care of business, trumpeter Malachi Thompson can strike a finely tuned balance between the roots of modern jazz and the wilder offshoots of the music's avant-garde--hence the Freebop Band's name. (And the last time he played in Chicago he was all business, playing with maximum fire and minimum jive.) But the buzz about tonight's performance centers on Billy Harper--who, along with George Adams and Jan Garbarek, was one of the three tenor saxophonists to dominate the 1970s. Harper, who was born in Houston, updated the tradition of the Texas tenor--Coltrane style. To the meaty, commanding sound of such tenormen as Herschel Evans and Buddy Tate, he added a searching spirituality that became the common denominator of all his music, from his searing solos in Gil Evans's and Thad Jones's big bands to the extended improvisations of his own small groups. In my life I've heard only a few saxophonists who could communicate such pure physical forcefulness: listening to Billy Harper was like standing at the edge of a hurricane. Reportedly, he has spent much of this decade in Japan; wherever he's been, this is his first visit to Chicago in perhaps a dozen years. Tonight, 8 PM, Center for Inner City Studies, 700 E. Oakwood; 268-7500, ext. 130.