<< I import the .WAV vocal track to chorus 1, bar -1, beat 1, but the vocals are behind a beat or so. >>
This is your vocal import settings. I downloaded the SGU and the Vocals. Thanks for doing that. I assume the vocals start at bar 9.

I adjusted the import settings to Chorus 1, beat 4, tick 0 and these settings properly placed the vocal track in BIAB. This import setting started the vocals at bar 9 and there was no time stretching during the import. I played the file with vocals at 118 bpm. Give this a try.

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Import audioi file settings.jpg (20.35 KB, 52 downloads)
DC Ron Song with audio in BIAB.jpg (262.46 KB, 51 downloads)

BIAB 2025:RB 2025, Latest builds: Dell Optiplex 7040 Desktop; Windows-10-64 bit, Intel Core i7-6700 3.4GHz CPU and 16 GB Ram Memory.