1) Select the A4 reference frequency, display mode (Needle or Strobe), and input level adjustment.
2) Select the temperament: Equal Temperament, Just Intonation, Pythagorean (Perfect fifths), or the Fiddle Sweetened modes.
3) If you select Just Intonation or Pythagorean, also select the root note for the temperament.
4) For the Fiddle Sweetened modes, the root note selector is disabled because the anchor is fixed by the selected mode.
5) Click START TUNING and play a steady tone. The note name and cents offset will be shown for the selected temperament.

This mode uses pure 3:2 fifths (Pythagorean tuning).

It is ideal for tuning a fiddle so the open strings and fifth-based double stops sound clean and consonant, with minimal beating.

Recommended GDAE fiddle tuning workflow:

Root = D (recommended), start on the D string

1) Set the Temperament to Pythagorean (Perfect fifths).
2) Set the Root note to D.
3) Tune the D string until the tuner reads 0.0 cents.
4) Tune the A string until it reads 0.0 cents.
5) Tune the G string until it reads 0.0 cents.
6) Finally, tune the E string until it reads 0.0 cents.

Alternative GDAE fiddle tuning workflow:

Root = A, start on the A string

1) Set the Temperament to Pythagorean (Perfect fifths).
2) Set the Root note to A.
3) Tune the A string until the tuner reads 0.0 cents.
4) Tune the D string until it reads 0.0 cents.
5) Tune the E string until it reads 0.0 cents.
6) Finally, tune the G string until it reads 0.0 cents.

In both cases, the strings are tuned in pure fifths, which is why all strings read 0.0 cents when correctly tuned.

These two modes are designed for traditional fiddle tuning where you want the open strings (G–D–A–E) to be tuned in pure 3:2 fifths for clean resonance and double stops, but want all other notes to match Equal Temperament for compatibility with other instruments.

Fiddle Sweetened (Anchor on D)
• D4 is locked to the Equal Temperament D (based on the selected A4 reference).
• G3, A4, and E5 are derived from D using pure 3:2 fifth ratios.
• All other notes are Equal Temperament.

Recommended workflow (Anchor on D):
1) Select Fiddle Sweetened (Anchor on D).
2) Tune D first until the tuner reads 0.0 cents.
3) Tune A, then G, then E until each reads 0.0 cents.

Fiddle Sweetened (Anchor on A)
• A4 is locked to the Equal Temperament A (based on the selected A4 reference).
• G3, D4, and E5 are derived from A using pure 3:2 fifth ratios.
• All other notes are Equal Temperament.

Recommended workflow (Anchor on A):
1) Select Fiddle Sweetened (Anchor on A).
2) Tune A first until the tuner reads 0.0 cents.
3) Tune D, then E, then G until each reads 0.0 cents.

Note: In these sweetened fifths modes, the Root note selector is disabled because the anchor is fixed by the selected mode.

If you are having issues with the tool not hearing your instrument, please click the link below to open an audio input test utility that will check if the audio input on your system has the correct levels and settings:

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You must grant the browser microphone permission for this tool to work.

The audio input level is displayed in a bar at the top-right of the tool.

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If no audio is detected or the audio input meter is maxed-out and no notes are getting recognized:

This tuner is designed to be used in a quiet environment.

It may not work well or at all with loud background noise or other instruments playing in the background.

To optimize the signal level coming into the tuner, I recommend that you first verify and adjust your system's microphone level settings as required to get a strong audio signal coming into the tuner.

If necessary, you can also reduce or boost the microphone signal level from within the tuner using the options in the Input level adjustment dropdown.

On Windows systems, you may also need to disable any automatic microphone noise reduction performed by the system audio drivers.

Noise reduction audio driver software may mistake continuous tones for background noise (such as fans or AC hum) and filter them out.

Open Windows Settings, search for Microphone settings, make any required changes, and then reload the tuner tab in your browser.

This tool was created by Michael Eskin.
If you find it useful, please consider making a contribution via my online tip jars:

The full source code for this tool is available on my GitHub repository.
The source is completely contained in the one file: tuner.html: