Cello tuner
C, G, D and A, one open string at a time, with the sound kept on your device.
- Nothing is uploaded
- Works offline after first visit
- Open source
- Free, no account. The microphone is on only until you press Stop
Tune your cello to C, G, D and A with your microphone, or press a string button to hear each note and match it by ear. The tuner shows which string it heard and whether it is sharp or flat. It is free, and the sound from your microphone is not uploaded: everything runs in your browser on your device.
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Play one string or note
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Done
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A cello’s four strings are a fifth apart: C2, G2, D3 and A3, from the thickest to the thinnest. The A is the first string and the C the fourth. It is the viola’s tuning an octave lower, so the open C vibrates at 65.41 Hz. Press Start the tuner, bow one open string, and the tuner lights the string it is closest to and shows how far off it is.
A worked example: you bow the open D and the tuner shows D with the needle to the left and “17 cents flat: tune up”. Take the peg up a little, bow a long stroke again, and stop when the needle sits in the shaded middle and the D button fills in. Tune the A first, then D, G and C, each a fifth below the last.
Cello strings are long and heavy and take a moment to speak, so use a long, slow bow and give the needle a second. The C is the lowest string and the slowest to settle. If the needle will not hold on it, press the C button and tune until the string and the tone sound as one, with no slow wobble between them.
The four open strings
The frequencies use the usual reference, A4 = 440 Hz, in equal temperament. They are the same numbers the page shows as a tooltip on each string button.
- 4th string, C: C2, 65.41 Hz
- 3rd string, G: G2, 98.00 Hz
- 2nd string, D: D3, 146.83 Hz
- 1st string, A: A3, 220.00 Hz
What this page does not do
- It is for standard C G D A tuning. A string tuned to something else, such as the A lowered to G, needs Chromatic, which shows the note name but has no string buttons.
- It hears one note at a time, so bow a single string and let the others rest.
- A fingered note is shown as a distance from the nearest open string, not under its own name. To read the name of a fingered note, choose Chromatic.
- Microphones pick up a low C quietly. Hold the device near the instrument and away from fans or other players.
How it works
- Press Start the tuner and allow the microphone. Cello is already chosen.
- Bow one open string with a long, slow stroke. The nearest of C, G, D and A lights up and the needle shows sharp or flat.
- Turn the peg until it says In tune, then tune the next string: A, D, G, C.
In your browser, not on a server
Your browser opens the microphone (getUserMedia) with its noise suppression and automatic gain turned off, and the Web Audio API hands this page about 85 ms of sound twenty times a second. Each slice is compared with delayed copies of itself (the McLeod pitch method) to find the period of the note, which gives its frequency to a fraction of a hertz; the reading is then dropped. The string buttons play a tone from a Web Audio oscillator.
Compared with upload-based tools: Tuner apps ask for an install and access to much more than the microphone, and many tuner websites are buried in ads and trackers. Here the sound goes from your microphone to this tab and nowhere else, and nothing is kept.
Verify it yourself. Give the page a short while after one visit to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Is a cello tuned the same as a viola?
The same note names, C G D A, but an octave lower: the viola’s C3 is 130.81 Hz and the cello’s C2 is 65.41 Hz, exactly half. A viola played against the cello list would read an octave sharp, so violists should choose Chromatic or use the violin tuner for the A, D and G.
How do I tune the lowest string, the C?
The C is C2, 65.41 Hz. Bow it with a long, slow stroke and wait for the reading; the page keeps the last note on screen for a moment after the sound stops. If the needle will not hold, press the C button and tune until the string and the tone sound as one. You can also bow the C and G together: a fifth with no slow wobble in it is in tune.
Can I tune the A string down to G for Bach’s fifth suite?
Yes. Choose Chromatic, bow the A string and lower the peg until the big letter says G with the needle centred: that is G3, 196.00 Hz. After the piece, bring it back to A3, 220.00 Hz. Chromatic has no string buttons, so there is no reference tone for it.
Is the sound from my microphone recorded or uploaded?
No. The pitch is measured by code running in this tab, about twenty times a second, and no sound is recorded or stored: only the last few pitch readings are held in memory while the tuner listens. Press Stop using the microphone to turn it off. Like any website, the host sees your connection’s IP address when the page loads, and the site counts visits with anonymous usage events that never include sound; the privacy page lists them field by field.
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