The Waipoua River system incises through sediments, for the most part, as opposed to bedrock. Pierre Boulez wrote his Grawemeyer Award-winning work "Sur Incises" for Sacher's 90th birthday. It usually incises the bark on the trunks or upper branches of the trees. A deep groove incises the midline of the symphysis of the lower jaws. In "Doorways" it reverses, turns inside out, and incises objects. "Incises" is charged with a bright, cold, hard brilliance, like a spray of crushed ice.