raddy,
Either that, create one yourself from scratch, use the Melody Maker feature to create one or change an existing melody by using the melody embellisher feature.
Click on the "Melody" tab at the top of the screen and you'll see the available options.
Forum member, Robert Stanley, created a video explaining use of the Melodist in Band-in-a-Box. The video is available on YouTube
+++ HERE +++ All the existing choices use midi. Are you wanting something different?