I'm doing a surround mix for a pipe organ recording and created a "chancel" bus and a "loft" bus since there are organ pipes at both ends of the church. One bus feeds to the surround front and the other the surround rear channels. What I'm finding confusing is that the levels are not correlating between the busses and the surround masters. If the "loft" bus reads -12, the surround rear reads about -18. If I bring the "loft" up, the surround rear increases much more. I can work with this but it seems odd. Can someone explain why, with all the volume sliders at 0.0, I'm not seeing unity gain?