Serenity has been categorized in three genre:
> Relaxing music piano
> Meditation music
> Lullaby music

Each has 5 looped music which is well enough to achieved your relaxation moment.

With five background nature that can be added one or all at the same time.
> Bird chirping
> Rain and thunder
> Calm ocean wave from the shore
> Campfire sound
> White noise

Timer setting: You can set the timer up to 60 minutes and the app will automatically close.