Nowadays we all know that every music video in Youtube (or any other video site) can be downloaded and converted to MP3 by using browser add-ons/web site. We all know that the song in video version is usually the same as audio version (in MP3 which sold on ITUNES or any other audio site). The question is why would I (as a buyer) buy the song if I can get the song for free?
My idea is just by putting the sound effects as BGM on the video so it encourages the people to buy the audio version to get the "free sound effects" version. The good example is found in Maroon 5-Pay Phone song where we can here the car struck sound effect in the video but we here nothing in the audio version. So it will differ the song from video and audio version and the people who watch video will know that they need to get the audio version to hear the "free sound effect" version.
NOTE: this is my idea. Everyone who use it should pay me!