The singer was a woman named Tatiana Moroz. I'd never heard of her before, though I gather that if I spent more time at Libertarian functions, I might have. As you can see from her website, Moroz is big on Libertarian politics.
As to the music, Moroz did a short four-song set, consisting of two original songs, a Bob Dylan cover ("Masters of War"), and a medley of "Greensleeves" and "A Home in the Meadow."
The performance was understated -- Just Moroz and her guitar. And I saw nothing fancy in her playing. It was pretty much standard strumming. But that voice. She sounds like a songbird. It was wonderful. I'm glad to have seen and heard her.
I bought her album, Tatiana (which for anyone interested is available from her web site). It's twelve original songs. The arrangements are more full than what we got at the convention (where, as I said, it was just Tatiana and her guitar). At times she sounds like a folkie, and at times she's adult contemporary. Sometimes she rocks a bit. The disc is well worth the price.
Here's a video of Moroz doing another Dylan cover, "Make You Feel My Love":
For what it's worth, I am not a big L libertarian, although my political thinking is strongly informed by libertarian philosophy.