As you progress, you hear some nice piano melodies as well as the sound of the soft wind. Also the sound of shrubs moving and some animals. Those are things that make the game more atmospheric.
The game is sometimes melancholic, sometimes mystical, sometimes funny, sometimes scary but mostly relaxing.
After you complete the game, another mode called "Noir" is unlocked and with it you play generally the same game but with another atmospheric black & white filter and it is night time. Also in Noir mode there are some surprising differences waiting for you.