The dance floor was empty but everyone was dancing

I'm setting up at a wedding and the room is packed, but when the first song drops the floor stays empty — except for one older couple slow-dancing in the middle, not to my music, not to anything I can hear. The speakers are playing a phone call between two people who keep saying 'we should've left earlier.' I check the mixer, everything's plugged in right, but the whole room is humming along to the call like it's the best song I ever played. I woke up still feeling the hum.