Karlheinz Stockhausen - Kontakte

Kontakte starts with a scattered series of chiming. Then proceeds to produce a shaking back and forth. The volume and tempos change sporadically in no obvious pattern or logical matter. Then a rough scratching and distant grumbling. Followed by a series of squawaking and more chiming. The noise slowing begins to speed up with a variation of more high-pitched chiming, shaking and pitter-pattter. A quick crescendo and decrescendo repeated several times and then a few dramatic notes played. The song then repeats more quiet chimes and is followed by a dramatic change of volume, tempo and a deep lowering of pitch. Then a circling variation of pitch which accelerates and decelerates. Then the volume fades out to the end of the piece. How can a piece contain such sounds that when standing alone are rough to the ear, but when put together seem to flow quite well?