My mom actually liked some of the music I listened to, and was always keen to explain some of the meanings I might not get. I recall her explaining who Alistair Crowley was after appreciating a wonderful guitar solo. She wouldn't go out and buy a Maiden album, far from it, but she had no problem listening to it with me in the car and appreciating various aspects of it.
My old man thought it was all garbage.
In any case, I did a one year bid at a non-denominational Christian school and got the full rundown on what music was evil and what was not. Turns out it all is. Yes, even Stryper.
If it has any occult themes it's evil. If it doesn't have any religious or moral themes one way or the other it's neutral, and therefore just as evil. If it has good, wholesome messages, they'd better be about God or it's still neutral, and therefore evil. If it praises Jebus and encourages salvation, it's still set to a beat that encourages young people to do naughty things, and is therefore evil. Makes the whole thing pretty simple to understand when you look at it that way.
The cassette I recall being passed around was a guy "going undercover" to a KISS concert to report on what he found.