Only use songs in your books that truly play an important role in the work of art. Never use a song just because you like it. In this novel, Joni Mitchell herself becomes a sort of character because for a couple of my characters her music articulates all of the heartbreak and pining they have felt throughout their lives. Mitchell is an artist who has always incorporated motifs of travel, loneliness, and heartbreak into her work so it's only natural that she be a musician featured in a book that deals with the same themes.
Also it is important to point out that when listening to a song that is this perfectly written I am not only learning some emotional truth about the characters' lives but I am also being inspired by such perfect writing as Mitchell's. Every line is a wonder. Surround yourself with art--music, photographs, paintings, films, whatever--that inspires you with its beauty and complexity.
Note: Don't let the French at the beginning throw you; that only lasts the first few seconds of the film.
Urge for Going, by Joni Mitchell