Musicians should be able to identify intervals. It goes a long way in improving your composing and improvising skills. If you find your skills in this area are rusty, or even completely lacking, there is something you can do. Go over to Michael Ossman’s Big Ears to sharpen your skills. For a more in-depth coverage of intervals, go to the Musical Intervals Tutor. Take some time every day to work on this and you’ll be hearing music in new way.