I think it's a natural process for writers to listen to music as they write, or to want to use song lyrics in their books, similar to the way movies have a soundtrack. As I was writing
Sadie's Mountain I listened to my Adele station, which I, of course, created myself on
Pandora.
In almost every song, I heard lyrics that reminded me of my characters and what they were going through. I also did research about "old timey" songs that Dillon would play to Sadie on his dulcimer. Music became a way for Dillon to communicate with Sadie. When she wasn't ready to hear his feelings for her, he played them to her on his iPod or he'd sing to her. It was a great tool to use in romance, in my opinion.
But you don't want to get in trouble or be sued. There's two ways to handle this.