Can someone please elaborate on Ducking Function? current version supports this - but it is unclear what function all these options accomplish? Can someone help?

I have yet to see proliferation of the apps such as media players that allow for this particular feature - to ignore other audio feeds and continue playing, regardless. So for example,If the media players playing the music station and I use your opens any audio source, Purpose sample YouTube video, the media player would not stop streaming at the radio station. I know for sure that this feature is available because I’ve seen this in one particular app that I will not mention just yet. Anyhow the app allows for an audio stream to continue sleep laying on top of any other audio without stopping. How could this be integrated into an app? thnx ed