wst3
Unveil, from Zynaptic, is amazing... not cheap, but it will remove more ambience, with fewer artifacts, than any tool I've tried.

Thanks! I'm going to have to try this.
 

williamsblackman

• i use iztope rx2for sermons to remove some of the room from the lav. mic my pastor uses it can remove some of the room 

 
RX2 is great for noise and other weird blips. Removing incorrectly wired patch bay noise is pretty snazzy. Along with the 50 and 60hz noise filters.

I think no matter which solution you try it will be tough since you said the horns were almost as loud as the choir.
 
If it is possible to get the choir together by themselves. Put headphones on them and record them by themselves while listening to the recording. This will get you the opportunity to mic them better and get the best recording.