Hi, I was the one who asked about Ryland by Julian Lage (on World's Fair). There are really quiet notes in the first and second measures of the song (if you are thinking of it in 6/8) starting on the sixth 8th note that goes A D A D A. And the next time it happens is on the down beat of the 4th measure and the notes are G E G E. There are other times it happens with different notes too. My first guess was that they were harmonics because some of them seem out of tune but I can't figure it out.
i'm hearing different ones than you are mentioning, like the one that comes out most prominently is the top of bar 2 (in 6/8) there is a loud F note (out of key). this is a hammer-on, from the wrong half of the string. this only happens acoustically, and it happens worse when you are playing in the middle of the string (or in the high fret range). if you do a hammer-on, it vibrates the correct half of the string (which gives you the note you want) but also the back half of the string (to the left of your left hand). on electric, you usually wouldn't hear it. but unplugged, the 2 notes will be of equal volume if the note is near the middle of the string. so in this case it is exactly in the middle of the string (12th fret) so both sides resonate equally. on a fretless instrument i think this would be the same note, but because it's fretted instrument, the target point to press is actually on the right bar of the fret, not the left. but the reverse note is happening from the other side, from the bar on the left side of the fret. so it's a slightly shorter distance. so you'll get F instead of E. this is not the note that you mentioned, but it seems to be the loudest and most obvious one right from the very beginning. the reason it is particularly problematic is because he's hitting it harder, for groove's sake, since it's the downbeat of the bar. really to avoid this in an acoustic close-mic situation is you have to try not to hammer as hard with the left hand, and do more of the work with your right hand. the rest of the quiet out-of-tune notes i believe are also unwanted reverse hammer-ons, but as we get closer to the left (the head? neck? sorry don't really know guitar terms, i am not a guitar player) the reverse hammer-on would be quieter, and higher. wherever you do a hammer-on, the lower (longer) of the 2 notes will be louder. that's just my analysis. i'm not really a guitar player