The term and the concept of Cuckoo Egg is quiet strange. When you download copy protected songs, you may come across Cuckoo Egg yourself. In the first 30 seconds of the downloaded song you may hear something other than the initial song which could be the cuckoo clock sound effects or a series of random sounds and noises that are free of any copyright ownerships. This happens for not buying the CD in the first place!
A Cuckoo Egg is an edited MP3 file that appears to be a copyright protected song being distributed via the Internet without the permission of the copyright owner. The initial portion of the song (first 30 seconds or so) will be of the real song. The remainder of the song however, has been overwritten by something other than the initial song; usually cuckoo clock sound effects or or a series of random sounds and noises which are free of any copyright ownerships. Cuckoo Eggs will have the correct file size and playing time as the original copyrighted MP3 file will have.
The Cuckoo Egg project was started to discourage people from trading copy protected music files online with Napster.