Over the course of making music, many bands find that they have songs that they can't fit into a release. Many times it is music that doesn't fit the mood of a release or they get lost in the process of compiling all the music into an album. It is very common and eventually these unreleased tracks see the light of day. These are often gems to the fans of the musicians and are where you can see these artists in a different light.
Post Punk band Pass Kluger have a gem like this for the world. This comes in the form of 3 amazing tracks in one release titled, The Lost Tracks. These 3 songs 12 minutes of melodies that present the sheer talent and passion that this New York/New Jersey band has.