As a guy who's been recording guitar bands for 14 years now, I have to admit to a problem: I have a painfully accurate awareness of tuning. This means I hear tuning discrepancies some people might not notice consciously; other people might just feel slightly uncomfortable without knowing why. Many of us who are engineer/producers have this blessing/curse. As a wee lad, I would turn on the radio and find myself thinking "Wow... Hendrix is out of tune there!" or "Rod Stewart's way sharp on this whole song" or "Why is that organ part so out of tune with the guitars?" And some classical orchestral music drives me nuts for this reason. Yup, a curse.
In less-commercial pop music (i.e. "indie rock") you can get away with more, if you're good. Sonic Youth and Pavement just wouldn't be the same if they were always in perfect tuning... but not many bands are capable of trumping imperfect tuning with their sheer force of personality, and you shouldn't assume your band is one of them.
In the studio, of course, my ear for tuning is a blessing... but if I get fatigued, it can transform into the Beast That Ate The Session, as my ears start playing tricks on me. I finally resolved to learn as much as I could about potential "tuning nightmares" so I could better defend myself.
To begin with, it is essential to grasp one iron-clad fact, or you will go insane:
It is impossible to ever get any fretted, stringed instrument "perfectly in tune". Nope. Can't be done.
Once you understand this, you can start dealing with the implications. Your life will become easier. I'll come back to this in a moment. Let's talk tuners.
THE INFERNAL MACHINES
Once in a blue moon I still get a band that actually doesn't use 'em.
Yeah, hard to believe, and this becomes tuning nightmare #1 when someone wants to do an overdub a few days later. Tuning by ear to the tape can be damned difficult, especially with the crazed noisy bands I often work with. I generally beg such a band to reconsider their tuner aversion, at least for the few days they are in the studio with me. Seems pretty obvious, right? (The single, amazing exception to this has been the band Zen Guerrilla, with whom I've made two albums entirely tunerless. Their tuning sense is so uncanny that I learned to just let 'em alone.)
I encounter three kinds of tuners: the kinds with little meters with needles that move (make sure you hold them horizontal!), the kind with rows of flashing LEDS, and those "strobe" types with a moving wheel and a flashing light. I haven't seen a strobe tuner in years, and never liked 'em much, though they work well if you can figure 'em out. Oh yeah, then there's those silly little "pitch pipes" like a mini- harmonica... avoid!
The most common moving-needle types are the Boss Chromatic ones, and they're pretty good, but here's a tip: the input jack is soldered directly to the internal circuit board, and these solder joints always crack eventually, which makes the tuner act "intermittent," with the needle jumping up and down. I have resoldered more of these in the studio than I can count; the plastic case comes apart easily, and you can resolder the jack in seconds. If you have one, check it: it may not be a "bad guitar cable" that's been frustrating you.
The little ones with flashing red and green LEDs that are often called "stage tuners" are rarely accurate enough for studio use — their only advantage is that you can read 'em without stooping and squinting. Hit that green LED, and you're done, right? Maybe. Some are okay. The cheaper moving-needle tuners are really not so great either. In my opinion the truly greatest innovation in tuners is the 19-inch-wide, single-rackspace multiple-LED type that you can read from clear across the stage. Korg makes some good ones. I finally had to buy one of these super-tuners for studio use; they are wonderful, deadly accurate machines. More on this in a moment.
SOME TUNING TRICKS
Here's another tip to make your life easier. You know how when you plug a guitar in and pluck a string, sometimes the tuner needle (or LED display) wavers back and forth and drives you crazy? And you have to pluck it every which way before getting a good reading which finally settles down? Do these three things:
1) switch your guitar to its rhythm (neck) pickup, if it has one;
2) roll your guitar's tone knobs all the way off, to remove all the highs; and then
3) pluck the open string right over the twelfth fret, not over the pickup. Try it; you'll be amazed.
Why does this work? Here's a quick physics refresher. The sound of a string being plucked is composed of a fundamental tone (the "note" itself, which also happens to be the lowest and loudest tone made by the string) mixed with a series of increasingly higher-toned, lower-volume harmonics, starting with the octave (or "2nd harmonic") and then going on up to include higher tones that are NOT octaves.
Each harmonic corresponds to the length of the string, divided by a whole number. The harmonic overtones are referred to by these numbers, and they correspond to those little "nodes" or dead spots on the strings where you can lightly place your fingers and get little chimey sounds. The 2nd harmonic or "octave" spot is exactly halfway along the string, right over 12th fret. The 3rd harmonic corresponds to one-third the length of the string, and can be found over frets 7 and 19, the 4th harmonic can be found over frets 5, 12 and 24 (or right over the neck pickup), the 5th harmonic over frets 4, 9 and 16, etc.
Several things to note:
1) The harmonics that are "powers of two" (2nd, 4th, 8th) are all octaves of the lowest, or "fundamental" note. To a tuner, they are the SAME note.
2) All the other harmonics represent DIFFERENT notes. It's the unique combination of fundamental plus these various harmonics that give any instrument its particular character or timbre.
3) How you pluck the string, where you pluck the string, and where the pickup is located under the string, determines the blend of "fundamental plus harmonics" that you hear. Pluck it near the bridge, and you get a twangy sound with lots of high tones. Pluck it near the middle, and you get mostly a deeper, more "pure" tone. Pluck it hard, and that initial burst of energy will cause more high harmonics. Put a pickup near the end of the string (at the bridge), and it will pick up more of those high harmonics; put it closer to the middle, and the fundamental tone will come through louder.
