This is a very tricky and complex subject. Most big name and expensive sampler/synths like Kontakt like to pride themselves for being accurate. Take bass for example. If you're having bass dropouts have you checked if the actual part is supposed to be played on a 4 string or 5 string electric bass or is it an acoustic? Do you know the correct range of notes for all those basses? How about a guitar vs a banjo? Same for all the horns. If you're going to be accurate and correct then you as the music producer have to know this stuff. This is where people will say all I want to do is make some music and have some fun. That's ok until you start getting picky and want things to really sound correct and good. Then you have to be aware of all these issues.

In our case here, the source midi is Biab. Check how Biab generates the different instrument parts. I can't tell you exactly how it works but sometimes Biab will produce notes that can be considered to be out of range for some instruments. What if you're doing a SRV song where he tuned his guitar to Eb so then an accurate low E bass note is the Eb? If you didn't set that up right that Eb will sound an octave higher or not sound at all. If you're missing bass notes change the bass instrument from a 4 to a 5 string and see if that helps.

This stuff is not easy sometimes. This is why we say Biab works best with a GM synth and then that always begs the question that has been asked countless times on this forum, "Where can I find a better GM synth?" And of course the answer to that is there's only a few pure GM synths around.

It's been said a gazillion times here, Biab is great for what it does but what it's not great at is acting like a full DAW for finishing a project. This is why everybody talks about moving the Biab tracks to a DAW for completion.

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.