How do I prevent a jingle which fades out slowly from being followed by a song where the artist starts singing immediately?

Create a Sound Code. Name it something like: Voice Open  and apply it to the songs that are Voice Open.

Then, on the Non-Music/Jingle to the Sound Code tab and then click the Voice Open  sound code.

This then tells Music 1 to not schedule any jingle with that Sound Code clicked in next to any Song that also has that Sound Code.