Robotic vocals have no emotional impact. Some of the greatest vocal recordings of all time featured less-than-perfect vocals. Percy Sledge was out of tune on "When a Man Loves a Woman." Ben E. King was straining in the upper limits of his vocal range on "There Goes My Baby." Hank Williams' voice wasn't capable of vocal gymnastics, yet his songs pack a powerful emotional punch. The trick is to know when a flaw enhances a performance.