Its saved by the artist himself and the recordlabel. Koffi listen sometimes to these unreleased songs at home. About the released songs, they hav each 5/6 different version and before releasing the album they pick the one who will appear on the cd-version. Last year I got the chance to listen to a different version of Wemba's song Reference with a fantastic guitar intro from Maika.
Theophile Badoana "Ndoki ya Molayi" filmed Koffi's Zenith of 1998, but I don't believe that he saved that video nor Sonodisc who has the rights of that concert, after that Koffi sold the images to them (They always receive the final version from the artist). If Theo has still that videotape, I will never release it. Because he doesn't have the right to do that.