Of course as a skeptic I don't believe in "magic", we can probably come up with a good rationale as to why music does what it does, although we may call it "magic" insofar as it has a powerful effect that is observable but has a mysterious cause - that's what magic is and to any phenomenon you can possibly imagine it is far more likely that you simply don't know what is going on than it is an exception in physics...always remember that.
The tribal chant thins fits. Music undeniably creates a sort of unity and bonding but we must ask ourselves if such a warrior bond would necessarily be stronger in the case of a musical ritual in a world of music than it would normally be in a world without appreciation of music. Perhaps music just creates a higher standard that isn't so meaningful if the standard that is required for the standard is taken away. There is good evidence for an entirely conscience-based and empathetic tribal and warrior unity that doesn't need music.
Still, something so apparently insignificant to evolution, yet that still produces such an effect could be described as "miraculous" in the loose sense of the word. I tend to subscribe to Steven Pinker's account of music as simply "auditory cheesecake" in the sense that the love of fat and sugar are adaptive, but cheesecake is not really and not particularly useful in itself, just as the modern manifestation of music isn't any more adaptive than any other talent that impresses people, except it combines impressiveness with ascetics. Nothing says that music is adaptive, but it is powerful, just like cheesecake.
But I'm inclined to call it "miraculous" in a loose sense of the word. if a true accident can produce this kind of unity and purpose http://www.youtube.com/watch?v=Zklqr1xj32Q then that is worthy of "magic" in as mystical a sense as I am willing to use the word.