There is a direct connection between the song melody, improvisation melody and the scale of the song. It is super important to understand this connection in order to be able to improvise along with the mood of the original composition and get a deeper understanding of how a melody line is composed. Once you get a deeper understanding you will be able to find your way around through any song without fear, in full confidence as you will be able to personalize a song, make the song sound different, interesting and powerful. Some compositions are connected to more than one scale.