For those interested, I had talked to Mike Gornick, the Romero veteran who shot Martin, Dawn of the Dead, Day of the Dead, etc. He told me that at least the two acoustic guitar/banjo cues I was looking for came from someone who worked on the film and was not credited. He was the sound recordist and also a bluegrass musician, so that solves that problem. I think Mike may have insinuated he may have supplied the other music I can't find, but it's certainly not DeWolfe.
