It seems there are, found this site tonight.
If I can do my music this way, using some of these ancient songs might add a surreal-bizarre element to the documentary. It might actually be more effective in a weird sort of way. Some of this historical stuff sounds down right bizarre in today's world, as is being in a garbage dump filled with barefoot children.
Update: Some the music on this site cannot be used for commercial purposes. Doubt I am making a commercial film but I guess there is that possibility. It is smarter to not worry about copyright issues. I will probably use the links below my music, PUBLIC DOMAIN and CC (can be used for commercial use with attribution), CC Remixing allowed (can be used for commercial use with attribution). I feel quite happy I have all this sound material to work with. I will be able to play with it next week in my video editing programs Adobe Premiere Pro CS6, Adobe Audition (hopefully).
Public Doman Music (1644 Tracks)
Commerical Use Allowed (11344 Tracks)
Commercial Use And Remixing Of Tracks Allowed (10776 Tracks)
Note* Have started to shoot a bit of video, that I MIGHT use in a doc.