|Christian metal band, Stryper, from their To Hell with the|
Devil Tour in 1986 (CC License).
It's definitely worth noting that the former employees also claim they were forced to participate in prayer sessions. That's an obvious no-no. The employer denies the allegation.
For a good video, check out this 2-3 minute video from the Saddleback Church (I know, I know... to be honest, I didn't expect an even-handed analysis either, but it's actually pretty objective): Is an employee or employer allowed to play Christian music or display Christian materials in their workspace?
HT: My friend Mike Chittenden emailed this one to me.