String change answered my question

I was about to post a question wondering what was causing my B string to buzz slightly when fretted, while no other strings had the same problem. Nut slot? Neck relief? Fret wear? I dreaded the chase, especially since the local guitar shop has changed luthiers, and I don't know how good or how expensive the new one will be.

Then I changed strings. Noise gone.

Of course I'm glad about that, and of course the rest of the strings sound nicer, too, but now I wonder what it was about the worn-out B string that caused it to buzz like that? I'd expect that from a wound string with unraveled windings, maybe, but not an unwound one. I was definitely overdue for a string change, but I've gone much longer between changes in the past.

I wonder how often guitars are taken to the shop, parts replaced and adjusted, strings changed, bills paid, noise gone, when it was really only the strings causing the problem in the first place?

. . . but now I wonder what it was about the worn-out B string that caused it to buzz like that?

Since you've changed the string, you'll never know for sure. My guess would be that it was the windings on the ball end - either some unraveling or maybe a minor gap (either of which can elude visual observation). My second guess would have been that a minuet piece of garbage had found a temporary home in the nut slot, but you said that it buzzed only when fretted.

Seaching for the source of a buzz on any guitar usually reminds me of the "blind guy in a dark room looking for a black cat that isn't there."

It is weird, what happens when strings go bad. I tried to return a brand new bass once -- I was certain the tuning gear was rattling. But the store just put a new string on, and it was perfect. So even a new string can make funky sounds, if there's something wrong with it.

I've had the same thing happen to me; fretbuzz, crappy action, weird noises, fixed by changing strings or going to a slightly different gauge. Sometimes it can change the tension on the neck just enough to fix small problems.