Your images do not at all match the song and do no service to the recording. Contrary to your pictures, it is not some sort of "black" song from the dark side but rather a beautiful song by an anonymous Italian composer about love for Christ. One need not share these views, but one should at least understand a bit about the song and its history before misrepresenting it to this degree.
this was one of the pieces of Laudario di Cortona from tuscany.It was written in 1200 more or less. This kind of songs in laudario were played by nomads musicians who went from village to village to sing the birth of Jesus.