A new play running in New York delves deep into the inner lives of professional musicians, providing a glimpse of the low-level politics, high drama, and endless sexual tension that pervade the industry. “Granted, most of the sex is in the past or the future, and the drugs are more medicinal than recreational. But it hardly matters… ‘Opus’ considers the matter of music making with an intimate, appraising eye, showing us the sweat, the drudgery and the delicate balance of personalities that lie behind the creation of a seemingly effortless performance.”