The most exciting of the label's inaugural issues is a new title from Art Ensemble of Chicago founder Roscoe Mitchell. In itself that is always a notable event, but this new group (with Mitchell's longtime rhythm section Jaribu Shahid and Tani Tabal on bass and drums along with new Art Ensemble trumpeter Corey Wilkes and the excellent young pianist Craig Taborn) stands among his greatest bands. They have all the role and bluster of Mitchell's Note Factory, but stripped down to an economic quinte…