Twenty years ago, a pair of psychologists hooked up a shoe to a computer. They were trying to teach it to tap in time with a national anthem. However, the job was proving much tougher than anticipated. Just moving to beat-dominated music, they found, required a grasp of tonal organisation and musical structure that seemed beyond the reach of an ordinary person without special training. But how could that be? Any partygoer can fake a smile, reach for a cheese cube and tap her heel to an unfamiliar song without so much as a thought. Yet when the guy she’s been chatting with tells her that he’s a musician, she might reply: ‘Music? I don’t know anything about that.’