When I saw The Waco Brothers play a noon set at SXSW a few weeks back, I could only think of one word to sum them up: fierce. When I later heard their new album, Going Down in History, that word asserted itself again. Although billed as cow punk, I’d call them rock with some punk and a touch of country thrown in. But whatever you call them, this band, led by Jon Langford of The Mekons, are an experience not to be missed. So go to Union Hall in Park Slope, brace yourself and catch The Waco Brothers. Chris Mills and The Distant Stars, who are new to me, will open the show.