You tune up, play a song, and the open G is flat. You nudge it back, bend a note, and now it's sharp. You retune between songs with your face going hot, certain everyone can hear it. The obvious villain is the tuning machine — it must be slipping — so you start pricing locking tuners. That upgrade fixes one specific thing, and it is usually not the thing that's wrong with your guitar.
Here is the reframe that changes how you troubleshoot it: a guitar stays in tune when every string can return to exactly the tension it had a moment ago. Drifting isn't the tuner failing to hold — the gears in a tuner essentially never slip. Drifting is the string getting stuck somewhere along its path and releasing unevenly. The fix is almost always about friction and settling, and most of it costs nothing.
The tuner is almost never the problem
A tuning machine is a worm gear. That design is self-locking by nature — the string's pull can't spin the gear backward, which is exactly why you can let go of the knob and the pitch holds. A genuinely faulty tuner does exist (a stripped gear, a loose post, a cracked button), but it's rare, and it fails in an obvious way: the knob feels gritty or spins freely. If your tuner turns normally and holds when you set it, it is doing its job. The drift is happening somewhere else.
Tuning stability is a friction problem, not a holding problem
Think about the whole path a string takes. It is anchored at the bridge, runs over the saddle, up the neck, across the nut (the slotted strip at the top of the fretboard), and finally wraps around the tuner post. Between those two anchors it passes over hard contact points — and at every contact point it can bind.
When a string binds at the nut, the slot pinches it and stops it sliding freely. Now you can have different tension on the two sides of that point: tighter on the tuner side, looser on the playing side, or the reverse. The guitar reads "in tune" for a moment because the playing length happens to sit at pitch — but that imbalance is unstable. The instant you bend a string, strum hard, or even just play for a minute, the string slips through the binding point to equalize, and the pitch jumps. This is the single most common cause of a guitar that "won't stay in tune," and it's documented by guitar techs and string makers alike, not folklore.
The friction-and-settling map
There are only a handful of places along that path where trouble lives. Learn the short list and you stop guessing:
- The nut slot — the number-one culprit. A slot cut too narrow, at the wrong angle, or left rough grabs the string and won't let it return.
- The string tree / guide (on many electric headstocks) — the little hold-down on the plain strings is another pinch point that can bind for the same reason.
- The saddle / bridge — less common, but a rough saddle groove or a sticky tremolo can hold tension the same way the nut does.
- The windings on the tuner post — not friction but slack. Too many wraps, or a sloppy wrap, leaves coils that slowly tighten under tension and pull the string flat. This is the one a locking tuner removes.
- The string itself — brand-new strings haven't finished stretching. Until they settle, they creep flat no matter how perfect everything else is. (This one is probably what just happened to you after Friday's string change.)
Notice what that list tells you: the famous upgrade, locking tuners, addresses exactly one item on it — the post slack. It does nothing for a binding nut, which is the most likely cause. That's why people install locking tuners and are disappointed that the guitar still drifts.
Read which way it drifts to name the cause
This is the part nobody lays out clearly. The direction and timing of the drift is a diagnosis. Before you touch anything, just notice how it goes out of tune — it tells you which item on the map is to blame.
| What you notice | What's almost certainly happening | Where to look |
|---|---|---|
| Goes sharp right after a bend or hard strum; tuning it down then makes it go flat the next time — it ping-pongs around pitch | The string is binding at the nut and snapping past the slot in steps instead of sliding back smoothly | Nut slot (and string tree, if you have one) |
| Everything creeps flat for the first hour, the first few days after a string change | New strings still stretching, and/or too much slack in the post windings settling | The strings themselves; how you wound the post |
| One string misbehaves while the rest are fine | That string's slot is binding, or that string has a kink from a sloppy wind | That one nut slot; that one string |
| The whole guitar drifts when the room temperature or humidity changes — cold gig, hot car, dry winter | Wood and metal respond to climate; the neck moves slightly and string tension shifts with temperature | Not a fault — re-tune to the room and let it acclimate before you play |
| Drifts only when you use the whammy bar / tremolo | Friction at the nut and the saddles, plus an unbalanced tremolo, all compounded by the bar's big tension swings | Nut + saddles + tremolo setup together |
The fix order — cheapest first
Work down this list in order. Most guitars are cured before you reach anything that costs money, and you should rule out the free fixes before you decide the hardware is at fault.
- Stretch and settle new strings. After tuning up, gently pull each string away from the fretboard along its length, then re-tune. Repeat until it stops going flat. This alone solves most "new strings won't hold" complaints — the strings simply hadn't finished stretching. If your trouble started right after a restring, do this first.
- Wind the post properly. Aim for a few neat wraps going downward toward the headstock, not a tangled pile — fewer, tidy wraps leave less slack to creep. Counterintuitively, more windings make tuning worse, not better.
- Lubricate the contact points. A little graphite from a pencil tip rubbed into each nut slot — or a purpose-made nut lubricant — lets the string slide instead of grab. Do the string tree too. This is the cheapest fix for the most common cause.
- Have a binding nut slot opened up. If lubricant only half-helps, the slot is genuinely too narrow or rough for your string gauge. A tech can widen and polish the slots in minutes; it's one of the highest-value, lowest-cost things you can have done to a guitar, and it improves action and intonation too. Don't file slots yourself unless you have the right gauged files — cut one too deep and you've created a buzz.
- Only now consider hardware. Locking tuners are genuinely useful — they make restringing fast and remove post slack — but they are not a tuning cure. If your drift was a binding nut, locking tuners will not fix it. Spend the money once you know the post was actually the problem, or because you value the faster string changes for their own sake.
The takeaway
A guitar that won't stay in tune is almost never a tuner that won't hold. It's a string that can't get back to where it started — stuck at the nut, slipping on the post, or simply not stretched in yet. Listen for the ping, watch which way it drifts and when, and work the free fixes first: stretch the strings, wind the post cleanly, lubricate the nut. Most guitars stop drifting right there. And if a proper setup opens up a tight nut along the way, you'll fix three problems — tuning, action, and intonation — for the price of one.