Honestech Photo DVD 4.0 - Manual (Page 58)

58. honestech ™
The added music file will be represented by a colored bar in the Music Track
below the Storyboard.
Depending on the length of the music file and slide, it is possible that the
background music file may play underneath several slides.
Each additional music file that is added to a slide in the Storyboard will be
represented by a different color in the Music Track.
Note: Adding a music file to a slide that already has music beneath it, will
cause that background music to be overwritten by the newest file being added.
You can identify which music file is below each slide by matching the color in
the Music Track with the colored end of each music file in the Background
Music Panel.