I know you are building a band hall, not an auditorium, But you might incorporate some ideas from this description of Ambassador Auditorium. You will need an auditorium at the high school anyway. If some of these elements are too small for your purposes they could be upscaled.

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The main lobby spans 4,000 square feet and features a massive, three-tier crystal chandelier. Rose onyx walls, African shedua wood railings and balcony-level handrails, a pure-wool carpet designed with an abstract reflection of the chandelier’s prism, and hand-rolled 24-carat gold leaf on the balcony and staircase under casings adorn the space.

Downstairs is the 3,168-square-foot lower lobby, which boasts two 24-carat gold chandeliers, Brazilian rosewood and rose onyx walls and another custom wool carpet. There are an additional 1,782 square feet of event space for up to 120 people, two multipurpose lecture and rehearsal rooms — one at 621 square feet, and the other at 945 square feet, accommodating 40 and 60 people, respectively — and gold and white dressing rooms with lighted mirrors, counter space and private restrooms with showers.