Dear Tony

Now I might be talking out of where the sun don't shine here - especially since I don't know the first thing about Macs/BIAB - but I had a similar experience with synths on a PC once. Second instrument being recorded.

OK. I was using Korg M1 Emulator. Turned out lots of their sounds are actually pairs of basic sounds being used together. And when you hit the MIDI Control part of the synth, the sounds themselves were split - one sound only came in at preset levels, either high or low. So you could make a composite sound from - say - choir and piano and have the choir only come in on the high notes (or low notes!)

Remembering I don't know (BEEP!) about BIAB, could it be something like that happening? One of the sounds you're using actually having a composite sound in with it that only kicks in at certain points?: If so, on the Korg there's a MUTE button and you can also just remove the sound from the pairing.

Just an idea, is all....

Yours respectfully

ulrichburke