Denver symphony orchestra Schedules 4 free concerts during summer in Denver parks. Listed, Straight Creek Journal Je I2, 1975 p.i5 Launches its first lU week summer night concert season at Red Rocks Ampitheater. Schedule. Post Roundup Je I5, 1975 p.6 Bruce Hangen proseoted to associate conductor. Straight Creek Journal Je I9, 1975 p.lk Red Rocks Symphony Under the Stars concert features violinist itzhak Perlman. Post Roundup Jy b, 1975 p.5 i