Dancin’, Yeah Prayin’ for this moment to last. By John Derbyshire For proponents of the theory that everything in the world exists for some good reason, disco music must present a conundrum. What higher purpose could possibly be served by this vapid, thrumping, affectless sound, dragging in its wake a subculture of narcissism, pill-popping, promiscuity both straight and gay, cheesy light shows, and the worst male clothing styles since slashed doublets and neck ruffs went out? Disco was so mockable it had barely got started before it was mocking itself — remember “Disco Duck”? The answer to the first of...