What links these pieces together are the wonderful voices Marie Yacoub from Malicorne, Milton Nascimento and Dulce Pontes. In recordings ranging from 1968 to 1999 all three songs use traditional musics and place the voice in the foreground, but underneath are beautiful arrangements that seem to both frame and free the voices.
The other theme is the move from a voice that is fragile and ethereal through a beautiful male voice to the power of Dulce Pontes (it is no surprise that she is a frequent collaborator with Ennio Morricone).
I would also say that Gabriel Yacoub's mutli-tracked guitar on "Le luneux" deserves mention for its simplicity and subtlety.