Bass Tuner
Tune your bass by microphone or by ear for standard EADG, with the low-frequency detection that catches out ordinary guitar tuners.
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A semitone at the bottom of a bass is 2.45 Hz wide
Pitch is geometric — a semitone is a fixed ratio, not a fixed number of hertz — so the same musical interval covers wildly different amounts of frequency depending where you are on the instrument:
| Note | Frequency | A semitone spans | One cent spans |
|---|---|---|---|
| E1 (bass) | 41.2 Hz | 2.45 Hz | 0.024 Hz |
| A1 (bass) | 55 Hz | 3.27 Hz | 0.032 Hz |
| D2 (bass) | 73.42 Hz | 4.37 Hz | 0.042 Hz |
| G2 (bass) | 98 Hz | 5.83 Hz | 0.057 Hz |
| E2 (guitar low) | 82.41 Hz | 4.90 Hz | 0.048 Hz |
| E4 (guitar high) | 329.63 Hz | 19.60 Hz | 0.190 Hz |
The low E on a four-string bass sits at the worst end of that. A whole semitone down there is narrower than a cent and a half at the top of a guitar — which turns out to decide how a tuner has to be built.
Which is why this cannot use a Fourier transform
A Fourier transform of N samples at 44.1 kHz splits the spectrum into evenly spaced bins of 44100/N hertz. Evenly spaced in hertz — which is the problem, because the thing being measured is spaced in ratios. Bins per semitone, where under 1 means a single bin is wider than the whole interval you are trying to resolve:
| Window | Bin width | E1 | A1 | D2 | G2 | E2 | E4 |
|---|---|---|---|---|---|---|---|
| 1024 (23 ms) | 43.1 Hz | 0.06 | 0.08 | 0.10 | 0.14 | 0.11 | 0.46 |
| 2048 (46 ms) | 21.5 Hz | 0.11 | 0.15 | 0.20 | 0.27 | 0.23 | 0.91 |
| 4096 (93 ms) | 10.8 Hz | 0.23 | 0.30 | 0.41 | 0.54 | 0.46 | 1.82 |
| 8192 (186 ms) | 5.4 Hz | 0.46 | 0.61 | 0.81 | 1.08 | 0.91 | 3.64 |
With the 2048-sample window most audio code reaches for, one bin at E1 is 8.8 times wider than a semitone. The transform cannot tell E from F, never mind flat from sharp. The same window at the guitar's top string manages 0.91 — still marginal, but 8 times better. This is a bass problem, not a Fourier problem.
You can buy your way out with a longer window, and the price is time:
| Note | Window for one semitone | Window for one cent |
|---|---|---|
| E1 | 408 ms | 42.0 s |
| A1 | 306 ms | 31.5 s |
| D2 | 229 ms | 23.6 s |
| G2 | 172 ms | 17.7 s |
| E2 | 204 ms | 21.0 s |
| E4 | 51 ms | 5.3 s |
Forty-two seconds of perfectly held low E, by bin width alone. No one is holding a note that long, and the string will have decayed long before.
And why the time domain gets easier as the frequency domain gets harder
Measuring the period instead of the spectrum inverts the difficulty completely. A low note has a long period, so a given fraction of a semitone moves it by more samples, not fewer:
| Note | Period | In samples | One cent moves it |
|---|---|---|---|
| E1 | 24.27 ms | 1070 | 0.618 samples |
| A1 | 18.18 ms | 802 | 0.463 samples |
| D2 | 13.62 ms | 601 | 0.347 samples |
| G2 | 10.20 ms | 450 | 0.260 samples |
| E2 | 12.13 ms | 535 | 0.309 samples |
| E4 | 3.03 ms | 134 | 0.077 samples |
At E1 one cent is most of a whole sample. At the guitar's top E it is a thirteenth of one — 8 times less to work with. The two methods have opposite signs for exactly the same reason: one measures in hertz and the other in seconds, and pitch is a ratio, so whatever hurts one helps the other.
This tuner uses autocorrelation, which works in the time domain. That is not an arbitrary choice — it is the only one of the two approaches that gets better as the instrument gets lower.
The price is latency. Autocorrelation needs at least two full periods before it can find one, and at E1 two periods is 49 milliseconds of sound against 6 at the top of a guitar. A bass tuner is inherently slower to settle, and if the needle here feels less immediate than a guitar tuner's, that is arithmetic rather than a fault.
How to use
- Allow microphone access, or use the reference tones.
- Play one string cleanly and let it ring.
- Tune up to pitch rather than down.
- Check tuning again after a first full pass.
Frequently asked questions
What is standard bass tuning?
E, A, D and G from lowest to highest — the same notes as a guitar's four lowest strings but an octave down. Five-string basses usually add a low B below, and six-strings add a high C above.
Why do some tuners struggle with a bass?
Because the low E sits around 41 hertz, near or below what many tuners and microphones handle well. Cheap tuners frequently report the first harmonic instead of the fundamental, showing a note an octave up and leaving you confidently in tune with the wrong reading.
Should I tune by harmonics?
It works well on a bass and is a useful cross-check, since harmonics ring clearly and are easier to hear against each other than fretted notes. Just be aware that harmonics reflect the string rather than the fretted intonation, so both are worth checking.
How often should I change bass strings?
Far less often than guitar strings, and it is a genuine matter of taste. New roundwounds are bright and zingy; older strings are darker and more thumpy, and many players deliberately keep strings for years because they prefer that. Flatwounds last longer still.
What is the difference between roundwound and flatwound?
The outer winding. Roundwounds are brighter, more textured under the fingers and harder on frets; flatwounds are smooth, mellow and much kinder to a fretless fingerboard. The choice shapes the sound more than most other decisions on a bass.
Why does my bass buzz?
Commonly action set too low, an uneven fret, or a neck that needs a truss rod adjustment as the seasons change. Some buzz that is audible acoustically disappears through an amplifier, which is worth checking before adjusting anything.
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