it's an older topic to the board so my apologies for reviving it, but there is an active fb page for the film and it's been going for a good while. i first learned of it when they had a crowdfunding initiative to give it some legs.
hxxps://www.facebook.com/LibraryMusicFilm/
there are lots of interviews and teaser materials are already present there. i can only assume a bit of this additional footage won't make it to the final cut, as modern audiences don't tend to go for film running times over two hours. personally i'm not a fb fan, but occasionally it does have some redeeming content.