The way a really good singing voice modulates and changes quality for different pitch ranges, for some reason I find deeply healing. Some wind instruments like the duduk also have this. It mirrors the way that an emotionally healthy person will allow different situations and actions by other people to bring out different sides of them, not mechanically but intelligently. They will sometimes act quickly and spontaneously, and other times sit quietly and think, and other times give themself the grace to admit being wrong and change their mind. This suppleness is a deeper kind of strength than being unchanging.