A cover is a new performance of a known song.
MMG represents companies that specialize in creating covers.
The cover catalogues include songs from the 50's till the most current hits.

You can get the cover in two versions: instrumental and with vocal, so you could edit it and easily add narration.
You can also get a cover which has a new arrangement.

Important: The price of a cover is less than when using the original performance (the master) but you still need to get the license for using the music and the words.