The building opens up pretty early in the morning for tourist to visit. However, the actual concert hall is not open unless there is a concert.
The hours vary. It depends on the concert hall's tour schedule. Most days it is open by 10am but the actual auditorium is usually only open to the public on concert days before the concert. Check the tour schedule. I'm not sure about gift shop hours but you can be sure it will be open on concert days. Box office is open Tues-Sun 12-6pm, 4pm on Monday's IF there os a Monday performance otherwise it is closed on Mondays. On Friday box office opens at 9am if there is a Youth concert.
Check their website. They have different hours for different types of tours and it's spelled out clearly there.
9:00am Monday through Friday
9 am on the weekdays
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