I don't think it is the essence of Ki, but a harmonization of sound with the vibrations of creation and life. Finding the sounds, the uses for the sounds, and applying them in a way that heals seems to be the most difficult journey in finding the sounds of kotodama, or any of the creative sounds.
I kind of liken it to a fine musical instument. A poorly played/ poorly made instument emits sounds that offend, while a well made, well played instrument brings pleasure.
Equate this to using sounds that move, heal, create strength or weaknes in movements, and it becomes a fascinating field of study.
The really neat thing, is how so many cultures have simular sounds with only minor variations.