Assuming things in 2013 are similar to 2012, you must have a valid Chase credit card (I don't know if has to be one of the Disney ones or not). At the Chase Lounge, in the Wonders of Life pavilion, they would hand out wristbands for IllumiNations viewing and/or seating at the Eat to the Beat concert. They were separate wristbands and you could choose if you want only one or both. They only had a limited number, so it was first come, first serve.
Last year's 3D Dessert party included reserved viewing of IllumiNations only. I think it was so folks could try out the Mickey Vision glasses that you got as part of the Dessert Party. Eat to the Beat tickets would make sense because the show times are 5:00 pm, 6:45 pm, and 8:00 pm. The first two shows are for before the party starts and the last show is during the party! I doubt anyone is going to want to miss out on the desserts and drinks to go see the concert!