Croma is a app with very simple and elegant interface that lets you play the music inside your local media library (Built-in Music app).
Besides rating, searching and filtering, Croma provides you more functions like looking for music with similar title within your music library, accessing and update the metadata such as skip count, play count and last played. Croma also allows you to copy or save artworks of the music.
In addition, Croma gives you the ability to set a timer to stop playing automatically after a specific amount of time. If you want, Croma can also enter full screen mode to keep the screen on and display information of the music when it is playing.
Moreover, with Croma you may customize home actions as shortcuts where 3D Touch is available. With those shortcuts, you can play music, set playing mode and set a stop timer with only one press on the home screen.
Because Croma plays the music inside your local library, installation of the Music.app is needed (Can be downloaded from the App Store). For how to add music to the library, please refer to support.apple.com/HT201593.