Lyric discussion by asSTARSfallx 

Cover art for Knotty Pine lyrics by Dirty Projectors

applestew, I think you're on the right track. To me, the sound that photographs make is something like nostalgia or a flood of memory. In this case, the nostalgia or memory has some mixed feelings associated with it. There are moments of clarity (i.e. "sharp precision"), but also captured in the photo are moments of reckless behavior (such as over abundance & indulgence - maybe getting too comfortable with a situation, taking a person for granted, or just being young & stupid). The clarity and the other stuff are all tied together in the photo and merged into one "sound" or memory. Perhaps the speaker uses the word sound to cleverly mask the meaning of the song, or maybe it is sound because it is a memory or an association of someone involved with music/the band/etc. Anywa, the two old planks of knotty pine seems like a metaphor for people who were once familiar to each other or familiar to the speaker - the fact that they're old suggests the passing of time, and the knotty part suggests that they've become hardened, more imperfect. I also like the use of the word pine as it has two meanings - pine as in the tree, and pine as in to pine away. As for the nails poking through, to me it means that looking at the memory (or hearing it - maybe sound = video) makes it sting a bit, and evokes a pain like nails puncturing through your skin. Just my thoughts, and a rather rough interpretation.