the hidden song archive:

A hidden song (also known as a "ghost track" or "easter egg") is a song on an album which is not listed on the album sleeve or jacket. On a CD, usually the song is accessed by playing the final track through then going through a brief moment of silence.

An unlisted track is different because the hidden song has its own track and can be directly accessed without having to go through the previous song, it just not listed with the other songs on the album on the back of the sleeve.

i seem to recall that there is a hidden track on pizzicato five's happy end of the world album or am i just imagining that? via the presurfer.