Another very simple distinction should be made between the words music and song.  Although they have to do with the same content area, they are not synonymous.  See below:

music X song

1. Music is a series of sounds made by instruments or voices in a way that is pleasant or exciting.  It also refers to the art of writing or playing music.

I often listen to music when I’m in the car.

I’m thinking about studying music at college.

2. A song is a short piece of music with words that you sing.  It also refers to the musical sounds made by birds and some other animals such as whales.

I love listening to pop songs on the radio.

Have you ever heard the song of the lark?