Cross-fading is a lovely technique to enhance the start and end of a course. It’s where music fades out, and as it does so, your voiceover comes in over the top. It’s easy to do in Storyline.
1> Take some music and use an audio application to add a “Fade out” effect. They are very often standard/built-in – just select the time, such as the last 2 seconds, and then click on Effects > Fade Out. Insert onto your timeline.
2> Insert your voiceover audio onto another Timeline area, then drag so that the 2 audio clips intersect as you want them to!
A simple and effective way to easily enhance the start (or end) of your course.