I write for all of the above and then a few more. Why do you write?
A picture says a thousand words, right? But what about music? Sometimes music has lyrics to paint pictures, other times you have notes to follow instead. What’s your musical genre? What story does your favorite song tell you? Is that why it’s your favorite? Music is important, even to writers, just because it’s another form of creative expression. It is communication, too. (And, incidentally, the flow of words in song lyrics or poetry is a good teacher for writers. They can influence how a writer uses their words and how their voice comes through on the page.)
So for a writing exercise, go through your music library and find a song to write to. Just one song. Think about the order of the words in the song, why they were put in that order. Think about the images the song uses; are they effective? What do you see when you hear the song? If there are no lyrics to prompt those images, why do you think the music draws those images out for you? Do you see anything in your imagination at all because of it? Do a free-write, just for the space of that song, while thinking about that song. Repeat the song if you get on a roll.