People tend to check in during these times:
Skip the elevator and hike the stairs. It's faster and a good pre-class workout. Down the stairs is a no-brainer.
Go up in the tower weedays noon to 12:45. Take the elevator to the top and climb up from there. If you can hear the music it's open. Great view! Earplugs rec for those with sensetive ears
You can hear (and see) the recital from 12-12:30pm when classes are in session. Take the elevator, then climb 2 flights of stairs to the Observation Deck!
If you're lucky you might catch sight of one of the falcon pair. But you'll more likely stumble over some random shredded bird part.