This has been asked for a lot, but I don't know how it can be done in Biab as it all seems to be deeply embedded into it by adding different time signatures together as "cells"
In RealBand it uses real time signature but if you save it to an sgu it reverts to 3/4 4/4 so you can't make a usertrack for RealBand with any real time signature.
I could do it with a script that you save the the wav of the usertrack wav that can be any time signature at all along with the ABC notation file that will give the bar location in the wav file of all the chords.
The script would then get the chords in your chord sheet by copying the chords from the ABC notation by accessing the Save As ABC Notation dialog "Copy to Clipboard".
It will then read the ABC notation file of the usertrack and randomly choose that matching chord/section from the wav file splitting, transposing, joining and setting the bpm then import into the RealBand track.
But if it's not possible with Biab without a total change at least try and get it in the Biab Plugin so it will follow any time signature or tempo map of the DAW, as RealBand has decimal point tempos but Biab rounds them down or up to the nearest whole.

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