Another way to do this is to put everyone in a chain, and have each person be listening to what the person before them was playing a few seconds ago. I wrote some software that does this, and anyone is welcome to play with it: https://echo.jefftk.com

It's open source: https://github.com/gwillen/solstice-audio-test

Here's an example with some informal singing my friends and I were doing this evening: https://echo.jefftk.com/recordings/2021-01-15-023012.wav (it makes ephemeral recordings)