The song playback screen of the music app comes across as a confused design. OS X and iOS have taught us that vibrancy reveals something underneath. This itself is not entirely unproblematic (http://forums.macrumors.com/threads...t-quite-work-in-safari.1939017/#post-22270280). Yet in the music app the vibrancy effect is used simply for decoration: You could argue that the entire music interface is intended to be represented above an image of the album cover of the currently-playing song, and this is what bleeds through the interface. Indeed, it remains in the interface in the Up Next view. But this isn't well-communicated, and seems superfluous. No doubt the design would look a little stark in the absence of these bleeding colours but it completely contravenes what the OS has taught the user so far.