The audio over section allows to you configure an audio channel that will overlap the existing audio:
audio_over
1. The 'Activate' field needs to be checked for the audio over to occur,
2. Specify the channel (if the value is 0, no audio channel is overlapped) and identify whether the audio over is for the entire event or from a specific start time for a specific duration,
3. Pressing the button next to the duration field will indicate 'until the end of the event',
4. It is also possible to specify the fading level.