Can you hear Bach’s faith in his music? Can you hear specifically Lutheran beliefs in his music? Or, if you can’t, could his contemporary listeners?
The answers to these questions matter because if you think a composer can communicate their beliefs through their music, then you are more likely to think that church music should be written only by Christians.
This also holds true for musicians. If you think that musicians can communicate their faith in ways that listeners can understand, then you might believe that church musicians should always be Christians.
Here’s what I think: composers usually can’t communicate specific beliefs in their music. But in certain scenarios, performers definitely can and do. That’s why it can be helpful for church musicians to be Christians but a composer’s beliefs are irrelevant in this context.