Stockhausen wrote this to accompany the DGG double-LP of HYMNEN (1967). Of all the "composition teachers" I have had -- including the great Nadia Boulanger -- I do not think I ever got advice this good:
Hide what you compose in that which you hear.
Cover what you hear.
Place something next to what you hear.
Place something far outside of what you hear.
Support what you hear.
Continue for a long time an event which you hear.
Transform an event until it is no longer recognisable.
Transform an event which you hear into the previous one which you composed.
Compose that which you expect next.
Compose often, but also listen for long periods of time to that which is already composed, without composing further.
Mix all instructions.
Gradually accelerate the stream of your intuition.