Write a brief essay defining "concept music" and provide an example

What will be an ideal response?

Music consisting merely of ideas for "pieces" the actual realization of which would either be impossible, ambiguous, or manifestly pointless.
The "pieces" often exist merely of instructions ("word-scores")
Pauline Oliveros's Sonic Meditations
"Take a walk at night. Walk so silently that the bottoms of your feet become ears" and "Become performers by not performing."
La Monte Young's Composition 1960 No. 9
"consists of a straight line drawn on a piece of paper. It is to be performed and comes with no instructions."