Doesn't continue playing previous audio

I'm using the plugin to play an alert sound when something happens in my app.

If Spotify (or any other music player) is playing in the background it is stopped to play my alert.
However when my alert has finished I want Spotify to resume playing.

I've tried using the release() function, but it doesn't hand back to the previous audio.

Is there a way of telling it to release to the previous app?