The opening act was Thomas Bartlett, the lead singer of Doveman. Meme-trackers may recognize him from his charming 2008 cover album of the entire Footloose soundtrack. He was a chatty performer, introducing each song with an explanation or anecdote.
He told the story of a song called “Angel’s Share” off the new Doveman album (you can hear it on their MySpace page). The Angel’s Share is the name of a tiny bar in Manhattan’s East Village, which is what Bartlett was originally writing about. He discovered that the bar is named after a piece of distillery jargon. From Wikipedia:
Angels’ share is a term for the portion (share) of a wine or distilled spirit’s volume that is lost to evaporation during aging in oak barrels. The barrels are typically French or American oak. In low humidity conditions the loss to evaporation may be primarily water. However, in higher humidities, more alcohol than water will evaporate, therefore reducing the alcoholic strength of the product. In humid climates, this loss of ethanol is associated with the growth of a darkly colored fungus, Baudoinia compniacensis, on the exterior surfaces of buildings, trees and other vegetation, and anything else that happens to be nearby
Comparing the Wikipedia article to the name of the bar and song, I see there’s some disagreement over where the apostrophe goes. I suspect that Wikipedia is correct, in that this is brandy or wine or whatever for all the angels, not one in particular.