You guys are confusing this issue. It doesn't matter what channel either Biab or Jabb is set for each instrument as long as they match each other . You can go into Biab properties, click on the channel tab and make them anything you want. In other words, you can set Biab to put the drums on channel 1 if you want even though the GM standard puts them on 10. You then put the JABB drums on 1 and so on for each instrument. Usually people keep the Biab channels set to the GM defaults and change their synths to match because if you start changing the channels in Biab, something will come up, you don't do anything with Biab for a few weeks, load in a different song maybe using the VSC and all your instruments will be messed up. All this confusion is the main reason people simply give up using non-GM synths with Biab. Styles don't always use the same instruments and you can spend time setting up JABB for one particular song, it sounds great, but you decide to just change the style for fun and oops, that one doesn't use guitar, it uses electric piano or whatever and you have to go into JABB and set it up for that channel manually just to hear what that style sounds like. Biab will use the same channel for multiple instruments depending on the style. That gets old after a while and most of us simply use a GM synth like the softsynth Forte or the hardware Ketron SD2 and forget about it. That's the beauty of GM, all the instruments match from one piece of software or hardware to another.
A sequencer like Real Band where you can use multiple synths is much more appropriate for JABB than Biab is.

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.