A ghost track, also called a hidden track, is a song on a CD that is unlisted. These tracks are preceded by minutes of silence after the final listed song of an album.
I first learned about hidden tracks from my dad. We were listening to a CD in the car, and he began explaining how some CDs have special secret tracks after the main album. We waited for a few minutes through the silence of the “end” of the CD and sure enough another song started to play. I remember thinking this was the coolest thing. He told me about a time he fell asleep with his headphones on while listening to a CD and jolting awake when track that was not supposed to be there blasted into his headphones. I was really taken with the whole idea.
