Many adults who sing lullabies for children use more of a soft voice with low volume. What I have been told is that playing an instrument or singing in piano (dynamics) isn't that easy. My experience is that this is true.
My understanding is that when you sing in piano you use a very physical technique. When adults (mostly untrained) sing lullabies it is another technique. It is a less physical technique.
What is the difference between singing piano (dynamics) and how most adults sing softly (with lower volume) when singing eg. lullabies?