Getting the first beat of a song set correctly is critical to determining how accurate the ACW is analyzing the correct tempo and chords in either version of ACW in BIAB you're using.

In the original version, selected using the ACW button in the Tools Menu, while the ACW program guesses a first beat, it is better to manually set it yourself. Do this by placing the moving bar line (curser) at the first beat and setting using the menu or shortcut (F6). This sets the first bar as a red line.

In the new version ACW that's accessed from the Audio Edit Window, Again, place the curser at the first beat of the song, Right click with your mouse and from the drop down menu, select "Mark this point as Bar 1 (e.g. for imported audio with long lead in).
Once you've determined you have the correct first beat set, Right click again and make the selection permanent.

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.