Hey Rob, strange I thought I replied to this question somewhere but now I can’t find it, very odd.

As Nate said the KU is the lowering of the tongue away from the roof of the mouth like when saying kookaburra, koala, kangaroo. You are not using your voice when playing but the action of the tongue is the same.

Close your eyes and say these words very slowly and become familiar with the movement of the tongue.

It definitely is not a breath attack. It is a release of built-up pressure in the air from behind the tongue when the tongue is lowered away from the roof of the mouth.

I hope that makes sense.

Cheers,
Greg