A bowl of pudding only has taste when I put it in my mouth — when it is in contact with my tongue. It doesn't have taste or flavor sitting in my fridge, only the potential. Similarly, the walls in my kitchen are not "white" when I leave the room. They still have paint on them, of course, but color only occurs when they interact with my eyes.
Sound waves impinge on the eardrums and pinnae (the fleshy parts of your ear), setting off a chain of mechanical and neurochemical events, the end product of which is an internal mental image we call pitch.
If a tree falls in a forest and no one is there to hear it, does it make a sound? (The question was first posed by the Irish philosopher George Berkely.) Simply, no — sound is a mental image created by the brain in response to vibrating molecules. Similarly, there can be no pitch without a human or animal present.
A suitable measuring device can register the frequency made by the tree falling, but truly it is not pitch unless and until it is heard.
Daniel J. Levitin in This is Your Brain on Music: The Science of a Human Obsession, acquired as one of the welcome hazards of setting foot into any of the Tattered Cover locations in Denver, Colorado (this one was Lodo). (Impossible to leave that place without dropping some coin.)
And offered this morning for Mr. BobcatRock of London -- Twitterer, Flickrer, and now Blogger (who of course immediately cemented my already growing affection when he said sweet things about detritus) -- who's suggesting that he just may finish that album this year.
Offered as a way of stating the obvious, which is to say: Please lay down those tracks, Mr. Rock, so that we can give them a listen.