On a Note 2, if I am listening to music or a video, whenever a notification comes in, the audio from the music or video is stopped to play the notification sound. This happens in any app I have tried, though I don't use the stock samsung apps much. MX Player for video, Pandora for music, as examples.
If watching a video, this means skipping back to rewatch the portion that had no audio.
Is it possible to have sounds from different sources mixed, rather than have the notifications take over the whole channel?