This is a standard Android Music Player with the following changes: 1. Volume control is set at a fraction of the current media volume. For example, CoPlayer can play at 50% of the current media volume. This is handy for playing background music at lower volume while listening to a foreground media at higher volume. 2. Will not mute other apps. 3. Will not be muted by other apps. To use CoPlayer: 1. Start your foreground app, Set its media volume. 2. In CoPlayer find and play some audio for your background sound. Set its media volume (it's always at a fraction of your foreground app media volume). Music CoPlayer has also been tested to work as specified above with my app "Meditation Creator" (https://play.google.com/store/apps/details?id=com. meditationcreator).