Up above, that’s Dave Gardner — I’m not sure I’ve got his last name right — sitting on his amplifier and playing guitar as commuters emerged from the North Berkley BART station last night. I asked him how things were going. “Cold,” he said. Were people responding to his playing, “Some,” he said. Mostly, he let his playing speak for him, and I got out of the way so I wouldn’t deter any passers-by from dropping a buck in his guitar case. I liked the music. I think the two numbers he plays here are takes on “All of Me” and “Sweet Georgia Brown.”