In reply to:


I guess it could also refer to the fact that the choir has heard a given sermon a million times already.



Yep, thats my point.

The Choir generally its assumed has heard the sermon many many times (especially if its a well worn issue), and therefore they are either:

1. Totally on side with the preacher and have been for a long time

or

2. Totally immune to whats being said and no amount of preaching will convert them.


another similar phrase is "you're preaching to the converted".