This is another one of those that skirts the line between suggestion and bug report. When you zoom in on a sleeping citizen, you get this nice easter-eggy lullaby tune, which is great. However, when you zoom in on multiple citizens sleeping closely together, you get this tune several times at once (with slight temporal offsets such that it becomes less relaxing and more chaotic). This is almost certainly not as it was intended—I think the effect of hearing the lullaby (just once) works just as well for multiple and single sleeping individuals, so it should probably always play once and exactly once.
(Spoiler!) Now, the new similar effect with eating citizens (that is indeed newer, right? I never noticed that in earlier releases) plays several times as well, but for that one it actually is nice that way, because multiple effects of cutlery clanging on plates actually is what multiple people eating together sounds like.