Can an employer enforce their decision to play only Christian music in the workplace?

We're now going to broadcast Christian music (1 cd per week) over the telephone system's speakers, and we'll no longer be playing out personal radios in our offices. This is a Human Resources company, with absolutely no religious affiliations whatsoever. Is it legal for my employer to force the whole staff to listen Dove Award winning Christian R&B for 37.5 hours per week here in the USA?