The Solstice Sackbuts will perform a free open-air concert of classical chamber music at 11 a.m., taking a musical tour through the centuries, starting with the Renaissance and Middle Ages, filled with interesting anecdotes about the composers and times and history of the trombone, ending with pop and jazz. Leslie Havens, of Waltham, plays bass and alto trombone for the Solstice Sackbuts. Alan Johnson, also of Waltham, plays soprano and tenor trombones for the group. David Lindsey, of Randolph, plays tenor and alto trombones for the band. The concert is sponsored by Brookline Bank in Waltham. In case of rain, the concert will be held August 16.