Band-in-a-Box RealTracks are unmastered audio and are generally quieter than a normal WAV file ripped from a CD or bought from a music store.

If you need a higher audio level for your WAV files, you can experiment with throwing a peak limiter on your master track to boost all the volumes. You can also investigate the process of Mastering, which includes raising the levels of a track to that which you'd hear on a CD.

Here's a link to an excellent article on Mastering, written by iZotope:
https://www.izotope.com/en/support/support-resources/guides/mastering-with-ozone.html


Cheers,
Deryk