What makes a great live performer? What makes people filing out of a concert utter such phrases as “mind-blowing,” “killed it” or “religious experience”? Is it the cult of personality, the overflowing charisma of the person onstage that can make you feel like you’re in the presence of greatness? Is it boundless energy and stamina, the kind that results in drops of sweat forming during the first song and puddles on the stage three hours later?