This is a great example of what Sufjan Stevens does so well on so many of his tracks. You start of with a simple melody and chord progression (basically two lines repeated over and over again), and layer on dozens of instruments, some playing major roles, some not even noticeable on the first few listens. With such small adjustments laid throughout, the song comes to life as a brilliant send-off to the youthful travels Sufjan and many of his fans have gone through. Many tracks on ‘Illinoise’ are written in a similar manner, but ‘Chicago’ is always a standout song and never fails to amaze.
Check it out here