"Ya, I am afraid this thread has lost me. It appears to conclude that BAIB can not play triads. Or that BIAB only plays a dominate chords over the fifth. That can't be true. I get that about modulation. Heck I have troubles with that also, so any suggestions for improvements are welcome. And I also understand that some selected RTs are more avantgarde and will stray from the chord sheet. But there are plenty of simple RTs which stick to triads when told to."

The original problem as I understand, is the songs starts in key of A, transitions to key of B after the transition real tracks are playing 7ths vice the intended plain old major chord. The OP suggests that a key change should not make the real tracks change how they are playing the chords, which is reasonable expectation. Many others have given him some suggested ways to get the result he is looking for. Then it got into a little tiff.

My wife asked if I had seen the dog bowl. I told her I didn't even know he could.