They do the music, but everyone is on mute (or at least they are supposed to be).Everybody just sings along at home.
It sounds really awful, due to differing bandwidth and connection speeds, to try to harmonize 60, 70, 80 devices that typically join in for a meeting. So they just mute everyone.
What's funny is to watch them sing as they are muted. Some folks really apparently get into it. I think to myself "poor neighbors..."