At a concert hall in the Chilean capital, Santiago, an 80-year-old man edges unsteadily down a steep staircase. With one hand he grips the metal bannister, in the other he carries a mug of hot water with a slice of lemon, as if heading to bed.
But when the red stage curtain is pulled aside for him, Luis Gómez, or JM as he is universally known, transforms in an instant. He skips on to the stage to a roar from the crowd and launches into a bolero, punctuated by hip thrusts and shuffling two-steps.
