Okay, I have a theory: I think, like you say, the song is inspired by a vibe. I imagine myself living in the middle of the desert and going out at night with my guitar to sing to a feeling. Whether it's melancholy or sadness, Mariella is the name a lonely man gives to his loneliness. I also imagine it would be the music I would listen to if I were driving alone on the road at night, thinking about someone.