Here in Brazil we have churches that allows members to sing songs from a book that we call it Christian Harp[1] as part of the worship, the result is a lot of people who can't sing to save their own life end up singing and musicians from the church try to find the song key and chords in real time, it ends up being a great practice to develop a good ear.

In this video you can see an example of how it is: https://www.youtube.com/watch?v=gF4onowI1xw

[1]: https://pt-m-wikipedia-org.translate.goog/wiki/Harpa_Crist%C...