It may be a long way back to recapture audiences lost to classical music through the disappearance of music education from the schools, changing lifestyles and perceptions of elitism, but the way back may be through places like Middle-earth. The average age at Saturday night’s performance of Howard Shore’s “Lord of the Rings Symphony” by the Cincinnati Symphony Orchestra at Music Hall appeared much younger than the normal mid-50s demographic. CSO staffers scrambled to handle the walk-up traffic just minutes before the concert, and it seemed that only the unsellable seats in the 3,516-seat hall (several hundred are limited and obstructed views) remained empty.