How to tune a guitar, bass, ukulele or violin online

What TuneBench does

• Tuner for string instruments: guitar, 7- and 8-string guitar, bass with 4 or 5 strings, ukulele, violin, viola, cello, mandolin and banjo. It recognises which string you play, or you pick one by hand.
• Chromatic mode: any note of any instrument, with its name, octave, frequency and the error in cents (±50).
• Needle, strobe or Pro: a classic needle; strobe bands that drift while the note is off and stand still when it is right; or a pro view with a zooming cents ruler and the pitch history flowing down the screen.
• Any concert pitch: A4 = 440 Hz by default, 432, 442 or 443 in one tap, or any value from 415 to 466 Hz.
• Reference tones: hear any string’s note to tune by ear.
• Metronome with tap tempo, 1–12 beats per bar, accents and subdivisions.
• Tuning log: when every string has been in tune, the result is kept in your browser; a tuning can be shared as a link.

How to tune

1. Open TuneBench, choose the instrument and the tuning.
2. Press Start and allow the microphone. On an iPhone or iPad sound can only start after a tap, which is why there is a button.
3. Pluck one open string and let it ring. TuneBench shows the note it expects, how far off you are and which way to turn the peg: Too low: tune up or Too high: tune down.
4. Turn the peg slowly until the needle is in the green zone (within ±3 cents). Hold it there for half a second while a bar under the hint fills up: the card flashes green, a short chime sounds, the phone buzzes, and the string gets a tick. TuneBench then suggests the next string; a string you picked by hand hands over to the next one by itself.
5. Repeat for every string, then check them all once more: tightening one string slightly changes the tension of the neck and the others.

If the tuner keeps picking the wrong string (a string that is several semitones off, or a new set of strings), tap that string’s button to choose it by hand. Tap it again, or Auto, to go back to automatic.

Always tune up to the note: if a string is sharp, go a little below the note and come back up. The string then holds its pitch better, because the slack in the peg is taken up.

Needle, strobe and colours

A cent is a hundredth of a semitone. The needle shows −50 to +50 cents. In strobe mode three rows of bands move to the right when the note is sharp and to the left when it is flat, faster the further off it is; when they stand still the string is in tune. The strobe shows even a fraction of a cent as a slow drift, which makes it handy for fine tuning and setting intonation.

The Pro view, modelled on the pro tuner of the Fender Tune app, puts a cents ruler at the top with a marker and the exact error in a bubble. Below it, the pitch of the last six seconds flows down the screen like a waterfall, newest at the top, inside a green corridor of ±3 cents and an amber one of ±15. Once the note has stayed within 10 cents for a moment, the ruler zooms in from ±50 to ±12 cents, so even a tenth of a cent moves the marker visibly; a jump away zooms back out.

Under the note you see the frequency you are playing in hertz and, in string mode, the string number and the exact frequency it should have.

The two round lights either side of the note show the direction at a glance, like a pedal tuner: ♭ lights up when the string is flat, ♯ when it is sharp (amber when close, red when far), and both turn green when it is in tune. Below the needle, a trace draws the last five seconds of the error, so you can see whether you are getting closer, overshooting or wobbling. The needle glides between readings and jumps straight to a new note. When the note dies away, the last reading stays on screen, dimmed, for about two seconds.

The chime and vibration can be switched off in the settings (When a string is in tune). While the chime rings, the tuner ignores the microphone, so it does not hear itself. On a computer, keys work too: Space starts or stops, 1–8 pick a string by its number, A goes back to automatic, P plays the reference tone.

Instruments and tunings

Strings are listed from the lowest (thickest) to the highest; the numbers are string numbers, the highest string being 1.

For anything else (a piano, wind instruments, a voice, an unusual tuning) choose Any instrument or switch to Chromatic: TuneBench then names the nearest note. Your instrument, tuning and A4 are remembered in this browser.

Concert pitch A4

A4 is the A above middle C, and every other note is counted from it. The standard is 440 Hz. Many orchestras tune to 442–443 Hz; some musicians prefer 432 Hz; baroque ensembles often play at 415 Hz. Choose the value your band or the recording uses: the string targets, the chromatic note names and the reference tones all follow it.

How the pitch is found

TuneBench uses the McLeod pitch method (MPM). It compares a short piece of the sound with itself shifted in time; the shift at which the waveform repeats is the period of the note, and one divided by the period is its frequency. Because it looks at the whole waveform rather than at the loudest overtone, it does not mistake the octave overtone for the note.

• Window: the piece of sound analysed depends on the instrument: about 0.17 s (8192 samples at 48 kHz) for bass, 7- and 8-string guitar, so that even a 31 Hz low B repeats several times in it; 0.085 s for guitar, viola, cello and banjo; 0.04 s for ukulele, violin and mandolin, which react faster.
• Search range: only periods that fit the chosen instrument are considered (in string mode, half an octave below its lowest string to a little above its highest), so a strong overtone cannot pass for the note an octave or two higher.
• Precision: the period is found to a fraction of a sample with a parabola through the peak, then measured again several periods later, which divides the remaining error by that number of periods.
• Clarity: a reading counts only when the sound is clearly periodic (90 % similarity, 80 % while a note is held) and louder than −70 dBFS, so room noise and speech do not move the needle.
• Smoothing: the needle goes through a “1€ filter”: it is smoothed hard while the note is steady and follows at once when it changes, so it does not jitter and does not lag behind the peg. A new note makes it jump straight there.

Voice processing that browsers turn on for calls (echo cancellation, noise suppression and automatic gain) is switched off, because it is made for speech and fades or distorts a steady tone. If a browser keeps it on anyway, TuneBench says so.

A hidden self-test checks the detector with tones that have overtones: guitar E2–E4, bass B0–G2 and violin G3–E5 at 48 and 44.1 kHz, bass notes with no fundamental at all, notes whose octave overtone is louder than the note, decaying plucks, noise, and silence. On clean tones the error stays well under 1 cent (in practice under 0.01 cent), and with noise or a decaying pluck under 0.2 cent.

Basses and phone microphones

Here is an honest limitation. Most phone and laptop microphones cut low frequencies: below roughly 80–100 Hz they hear very little. The open strings of a bass sit at 31–55 Hz (B0, E1, A1), and the low strings of 7- and 8-string guitars and cellos are near that range too. So the phone barely hears the fundamental of these notes.

TuneBench still tunes them from the overtones: a string’s overtones (2×, 3×, 4× the frequency…) together repeat exactly at the period of the fundamental, and that period is what MPM measures. This is why the low B of a five-string bass can be tuned with a phone at all. It works when the overtones are strong enough: pluck firmly, towards the bridge, with the bridge pickup or a bright tone. With flatwound strings, a very soft touch or the tone knob turned down, the reading may be unsteady or missing.

The surest way for a bass or an electric guitar is a cable: an iRig-style adapter or a USB audio interface. Choose it in Input (the list fills once the microphone is allowed).

Tips for a steady reading

• Play one string at a time and mute the others; a chord has no single pitch.
• Read the needle a moment after the attack: every string sounds slightly sharp at the start of the note and settles as it rings. TuneBench does not count the first moments of a pluck towards “in tune”.
• Hold the phone 10–30 cm from the sound hole or the amp; a quieter room helps more than playing louder.
• If the input level stays low, a hint appears. Bring the instrument closer or raise the gain of your audio interface; if the meter turns red, lower it.
• Electric guitars can be tuned unplugged near the microphone, but through an interface the reading is steadier.
• The 12th-fret harmonic of a string is an octave above it and very pure; in chromatic mode it is easy to compare with the fretted note to check intonation.

Metronome

Choose 20–300 beats per minute with the slider or the − and + buttons, or tap the tempo with Tap tempo (the last five taps count). Set 1–12 beats per bar, and tap a beat to switch it between accent (a higher click), normal and silent; a silent beat helps you practise keeping time yourself. Subdivision adds softer clicks between the beats: eighths, triplets or sixteenths.

The clicks are scheduled ahead on the audio clock, so they stay even when the page is busy, and the screen stays on while the metronome plays. It shares the sound with the tuner, so both can run at once. The metronome used to live in TimeBench; its settings move here by themselves.

Privacy and offline use

The microphone signal is analysed in your browser a few times a second and then forgotten: nothing is recorded, uploaded or sent anywhere, and the page makes no requests to other sites. Your instrument, tuning, A4, metronome settings and the tuning log are kept only in this browser. A shared tuning link contains only the instrument, the tuning, A4 and the error of each string.

Once you have opened TuneBench, it works without an internet connection, and it can be installed as an app from the browser menu.

Frequently asked questions

How accurate is it?

The detector itself is accurate to well under one cent. In practice the limit is the string: its pitch drifts by a cent or two as it rings and with how hard you pluck. The green zone of ±3 cents is tighter than most people can hear.

Why does the needle not move?

Check that the button shows Stop (the tuner is listening), that the input level moves when you play, and that the right input is chosen. If nothing moves at all, the browser may have blocked the microphone: allow it in the address bar and press Start again.

Why does it show the wrong string?

It picks the string closest to what you play. A string that is several semitones off may be closer to its neighbour; tap the string you are tuning to choose it by hand.

Does it work on iPhone?

Yes, in Safari and other browsers on iOS 14.3 or later. Press Start (iOS starts audio only after a tap), allow the microphone, and keep the page in front: the browser pauses it in the background.

Can I tune a piano or sing with it?

Yes, in chromatic mode, for checking single notes. Piano tuning needs stretched octaves and a lot of skill, so use it only to check a note or two.

Why did the string not get a tick while the reference tone played?

On purpose: the microphone hears the reference tone itself, which is always exactly in tune. Stop the tone, pluck the string, and hold it in the green zone.

Can I use the metronome and the tuner together?

Yes. They share one audio engine. The tuner may pick up the clicks between notes, so for careful tuning stop the metronome first.