Another point is like Matt said, there's a lot of "moving parts" involved with this. If you've changed midi synths or like some, you have a bunch of them and switch them using Biab 2012's ability to insert a different VSTi with each instrument, then you have to realize each synth has it's own volume settings. A software synth is exactly the same as my Kurz hardware synth. They use precorded samples and just like our RT's, those samples are recorded and created by the mfgr at slightly different volumes so this problem can not only be caused by changing a particular synth, it can be caused by specific patches in that synth. People will comment here that synth A has better sounds but they like using synth B because the soundset has better overall balance and requires less tweaking to achieve a good overall mix. Welcome to the world of digital audio, it can be very tricky stuff. The only way to stop this from happening is to not play your songs as Biab files because those can change but to render them as audio files and then they are set forever just like buying a CD. If you're like me, I like to play my songs as Biab files because I can experiment with them but I also realize that will change the mix.

Bob

Biab/RB latest build, Win 11 Pro, Ryzen 5 5600 G, 512 Gig SSD, 16 Gigs Ram, Steinberg UR22 MkII, Roland Sonic Cell, Kurzweil PC3, Hammond SK1, Korg PA3XPro, Garritan JABB, Hypercanvas, Sampletank 3, more.