Almost 30 years ago, a new sound began bubbling up in small venues around Chicago — jazz clubs sometimes, but punk clubs and arts centers and other less defined spaces too. Cornet player Rob Mazurek was one of a small coterie of players, some of whom were members of the dubby “post-rock” (remember when that was a thing to aspire to be?) group Tortoise, and others who were experimenting in other ways, but all of whose music was blurring and erasing the boundaries between jazz, rock, electronic music, modern composition and improvisation.