This post is strictly about guitar setup; for those who care naught for guitar mechanics, nothing here to see. Catch you next time.
I had an interesting guitar setup experience recently. If you have even moderate experience with guitar setup, this will probably all be old hat. (And if you have none, you probably don't care. So who's reading? Hmmm.)
I got my electric a year and some ago. It's a knockoff of a Gibson ES-330:
I like it fine. As I got it, it had some relatively high-gauge strings (11s, probably). Being new to electric, I had nothing to go by, so I used that guitar as-is. I had a setup done at one point, but didn't have it restrung. During one of my lessons, tho, we were talking about bending, and my teacher had a go on my guitar. "Lighter strings, dang!" was his recommendation, so I had one of the shop guys put on some lighter ones (10). It was sort of a rush job, which more-or-less explains the rest.
The lighter strings were a definite plus. However, it seemed to me that the guitar had developed a slight buzz. (This is where the experienced folks say "duh.") I kept thinking I should take it in for another setup, but didn't get around to it.
One night, tho, I was at guitar school (not to be confused with lessons), and the owner dude (Jay) introduced Ryan, a new guy they had. Ryan was a guitar builder, Jay said, and was open for business. Specifically, you could bring him your guitar for repair or whatever. It was the same price as taking the guitar to a shop, but -- the cool part -- you could watch and, if you wanted, Ryan would teach you to do what he was doing.
So I took my guitar in and watched Ryan do his thing. The first thing he did was have a look at the alignment of the neck and body. Dead straight, he noted. Not good, I asked? Not what you want, he said. The neck should actually "up-bow" a tiny bit (we're talking very small fractions of an inch here).
That way, there would be enough clearance between string and fret as you fingered notes, but the strings wouldn't actually touch the frets (the source of the buzzing). When I'd had lighter strings put on, there was less tension on the neck, so it flattened out a tiny bit -- enough to introduce the little buzzing I'd noticed. Ryan adjusted the truss rod (whatever that is) to loosen it just enough to compensate for the lighter strings. Presto, done.
Ryan then tuned the strings. He started with a gross tuning -- setting each open string to its nominal pitch. But he explained that the in-tune-ness of the strings was not perfect up the fretboard. For example, in a simplistic guitar design, fretting at the 12th fret would not get you an exact octave. Among other reasons, fretting the string stretches it ever so slightly, which of course affects its pitch. (More)
To compensate for this, on electric guitars (and, like, violins and stuff) have a way to micro-adjust tuning. On some guitars, like mine, the strings lie over a saddle arrangement that has screws to adjust the string, known as intonators. Here's a little more detail:
[I]f the bridge is placed at exactly the theoretical position (nut - 12th fret distance multiplied by 2), the fretted notes will get progressively sharper the further up the fingerboard one plays. This is because fretting the strings stretches them by a small amount, raising the tension and therefore the pitch of the notes produced. Action height is normally lowest at the nut and highest at the last fret, so the sharping effect increases with distance from the nut. To compensate for this, length is added to the string at the bridge end. The amount necessary varies from string to string, generally increasing from treble to bass. "Intonation" means adjusting this compensation until the open notes and the 12th fret notes of each string are exactly one octave apart. (Paul Guy, "Tuning the Guitar")The intonators on my guitar look like this:
Ryan fretted each string at the 12th fret and then adjusted the intonator until the string was in tune at that fret. The resulting stair-step arrangement of the intonators is typical. There are two such stair steps here, one for the wound strings, one for the non-wound strings; note that in each case, the heaviest of the strings is the longest. (On acoustic guitars, the bridge often has different bevels for different strings. Some, like my Takamine, have a split bridge whose arrangement approximates the stairs steps of the intonators.)
Ryan offered to let me do some of this adjustment. I declined, although I'm not sure why; it wasn't a particularly exacting job, nor could I screw up the guitar. (Much.) I was just happy to see what he was doing and be able to get explanations and ask questions. In the end, because the job was so quick, I ended up paying even less than I would have for a regular setup.
I don't have enough guitars that I can keep one around as a junker to practice all this stuff on. It's inevitable that I'll have one eventually, tho. As all guitar people know, there's always another guitar waiting to be bought. :-)