A sure guarantee that this was bogus (really, any reasoning is required at all?) was that it did the rounds applied to John Denver, Annie Lennox and others.
Basically, they relied on Satan (oh yes) for their musical ability (I knew it) and any JWs in the audience would be asked to leave because ... (drum roll) ... they blocked the signal to Satan so couldn't perform with them present!
Anyone else remember that gem?
I also remember getting lists of disallowed songs including 'Bridge Over Troubled Water' by Simon & Garfunkel which they claim was about drugs.
Not like the Kingdom Melodies cassettes which you really needed to be ON medication to listen to.