I thought I would describe this in case another player is plagued by a weird unexplained back buzzing as I was.
After a bit of detective work I discovered that I had a ‘back buzz’ on my 6th string when I fretted at the 4th fret, and also if I had a capo fitted at the 4th fret.
This Bryan Kimsey YT video nicely shows what I was experiencing:
https://www.youtube.com/watch?v=yXUZmRmQ030Note that in Bryan’s video his back buzz was occurring after a re-fret with SS frets. My buzz was happening with the standard as-fitted Taylor frets. So I don’t think this type of buzz is dependent on type of frets that are installed - it can happen with any frets.
Anyway, the cure turned out to be straightforward. I discovered that my replacement bone nut 6th string slot had been cut to low by the expensive Luthier ((thanks for that) and there was hardly any clearance at the 1st fret. I partially filled the nut slot using the baking soda super glue technique (see Stewart Mac video), and carefully re-cut the slot this time with acceptable clearance. The annoying back buzz had departed.
