One of the most complicated tasks in film production is integrating the soundtrack with the video. It's no problem in an unedited start-to-finish transfer from tape to disc, but audio continuity becomes rather complex when merging scenes from several sources or just editing sections from a single tape. You can remove a few seconds of video without anyone noticing, but if a few seconds of music are also gone, everyone will notice. You can try fading one sound out while fading another in, or just watching where you're cutting the audio when you edit the video to keep distractions to a minimum.

To avoid abrupt audio shifts when changing scenes, you can insert a sound effect.
The blue line here indicates the sound level of a helicopter engine, which fades
in at the beginning of the scene and fades out at the end.