The Horror

I dig kids and have been told about the joy of hearing their delightful
laughter and exuberant singing but trust me, when you neighbor buys a
karaoke system to keep their 6 year old entertained ALL DAY LONG, you
start looking for the circuit breaker quick.

Does anybody know if there is a particular age in which kids grasp the
concept of singing in a single key?

This is going to be a long winter.