When I go to church I like to sit in the rows where there aren't any people directly behind me. Once in a while you will get some guy who couldn't carry a tune with an earthmover who is so excited about Jesus that he tries to belt out every song like a Caruso wannabee and he'll sing into your ear at 100 decibels in a whole different key than the rest of the congregation. As a musician, I find that quite unbearable.
As my eternal punishment for being annoyed by these enthusiastic worshipers, I'm sure God will assign a whole group of these people to sit right behind me forever in the eternal Heavenly Chorus.
He that has ears to hear, let him cover them.
I guess if they are going to be there forever, they will probably learn to sing in the right key.... eventually.
Check over your shoulder. It might be me singing off key. I have a daughter whose hearing is awesome and she has, I think, been gifted with perfect pitch. Even as a toddler in my arms as I sang in church, she would slap her hand over my mouth. I got the message. Maybe that is my antipathy to heavenly choir singing. On the other hand, if I could write the lyrics, that would be cool.