These disco-influenced rock songs cover two distinct periods. Some came in the immediate wake of the disco craze, when veteran rockers like KISS and Rod Stewart tried to capitalize on the hot youth trend. (The miracle is, cynical or not, the results were amazing and arguably their best work.) Others came 15 or 20 years later, after those songs once met with cries of “Sellout!” became incredibly influential. Just listen to the Scissor Sisters’ take on “Comfortably Numb,” a genius cover that infects a musty old classic rock standard with a pulse.