What is pitch and where does it come from? This simple question has generated hundreds of scientific articles and thousands of experiments. Almost all of us, even without musical training, can tell if a singer is offkey; we might not be able to say whether she is sharp or flat, or by how much, but after the age of five, most humans have as well a refined ability to detect tones that are out of tune as to discriminate a question from an accusation (in English, a rising pitch indicates a question, a straight or slightly falling pitch indicates an accusation).
