Hidden track意思

"Hidden track" is a term used in the music industry to describe a song or track that is not listed on the album's track listing, but is included after a period of silence following the last listed track. These hidden tracks are often found on CDs and are a form of musical Easter egg. They can be anything from short snippets to full-length songs, and they are sometimes used to provide bonus content for fans or to include material that the artist wants to include but doesn't want to promote as part of the main album. Hidden tracks were more common in the CD era, as they could be easily added to the end of a CD without taking up space on the vinyl or cassette versions of the album. With the advent of digital music and the ability to skip through tracks with ease, hidden tracks have become less prevalent.