I'm with what Henry says in its entirety. I regularly attend a singaround which is very welcoming to the extent that any newcomers are very much encouraged to contribute. Anything goes but it's pretty obvious by what the regulars are singing and what goes down well. We get older pop songs, self-penned material, poetry, and mostly of a very high standard. As long as the regular folk scene material dominates and goes down well, as it does, then we prefer the variety and standard we aim for.
I too have been downhearted by poor use of a phone, but a young lass yesterday very reluctantly eventually had a go and she had a beautiful voice. She might just be encouraged by the response to have a go at the type of material that dominates. Either way it's a win win from our point of view. Casual drop-ins are always very complimentary at what they hear.