Melodies are copyrightable but not chord progressions.

With BB you are free to use everything there for your own. If you use the demo songs.... simply do as you did and change the melody. I have considered doing that myself but so far have not.

Everything BB creates for you is considered to be your creation and you are free to copyright it and use it.

I have a number of songs in music libraries that were created 100% in BB and those songs are listed under my account as being written by me. Copyright with pubs and libraries can work slightly different from just an individual filing a copyright. Technically, I don't own them any more, the publisher does, but I'm still the writer and have the rights accorded in the contract. Same protection but a different path to get there.

So yeah, feel free to do what you did without worry.

BTW: Cool song interpretation. If you hadn't titled the thread infringement, I would never have guessed. And..... BTW, it's not infringement.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.