I'm transcribing Tommy Emmanuel's rendition of Classical Gas. At 1:19, during the C chord, there is an apparent C3 sounding twice. But as can be seen in the video, he's nowhere near string 1 fret 8. I examined some harmonics available around the fingering shown in the video, but the closest thing is a C4. What really fries my brain is that it certainly doesn't sound like a harmonic. It sounds very much like string 1 fret 8. Is this being caused by a resonance in his particular guitar, or is there some trick he's employing that I'm not aware of? I'm completely bewildered.
Update: I think another possibility is fret buzz