... Another indication of what a powerful social factor Music has been for probably about as long as Homo Sapiens has been schlepping around on this Planet.

I have yet to see the "Gangs" flic, but intend to.
The subtle cultural reversal of "GarryOwen" as alluded to here reminds me of a story i saw on TV (supposedly true) of a Scots Piper who was captured at a Castle his Clan was trying to hold while the rest of the Clan was out looting & plundering or whatever.
His Captors forced him to play from the tower as his Clan's fleet sailed back in so as to lure them into a trap; he instead played an air that his friends recognized as a warning, and escaped.
The infuriated foe cut off the Pipers hands in retaliation, and he died a few days later. A skeleton was recently discovered at the Castle with it's hands missing, which tends to lend credence to the ledgend.

The communicative power of Music is one of those things I think we oftimes overlook.