A couple days ago I had to Google, “What do middle aged women wear to indie rock concerts?” I came up with lots of pics of denim and leather and high-heeled boots. Not much different than what I expected young women to wear, except fewer backless shirts.

When I picked up my also-middle-aged friend (ok, not really, we're still young! Middle age means, like 79, right?) she was wearing the requisite jeans, tank top, jacket. I'd opted for...