“Yet Disney Hall is not what it could be. Panicky cost-cutting measures during construction left out elements that would have made the exterior and lobby more dazzling and the hall more flexible. The Music Center, which maintains the hall, seems in danger of taking the venue for granted, not eager to invest in it when it can bask in glory by doing nothing. The Metropolitan Transportation Authority is planning a subway line under the hall, raising concerns that train vibrations will spoil the sound.”