Instrument Tuner — Mic Detection

An instrument tuner with microphone pitch detection that tracks the fundamental of a plucked or bowed note and reports the cents error against a chosen reference. Pitch analysis runs in your browser with the Web Audio API on a 4096-sample frame; nothing is recorded or uploaded.

How to use it

1. Pick a preset from the Tuning Preset menu. Guitar, bass, violin, viola, cello, ukulele, mandolin, banjo and world instruments each load their own string list; Chromatic accepts any note. String rows show targets in hertz, so low E on a standard guitar reads 82.41 Hz.
2. Start microphone detection. Click Start Tuner (Microphone) and allow access; the badge switches to Microphone Live. Simulate Audio plays a synthetic note if you want to see the gauge work first.
3. Play one string or one sustained note at a time. Palm-mute the other strings, use a normal attack, and give the note about half a second to settle. Analysis refreshes every 50 ms.
4. Read the note, the cents badge and the needle. The gauge spans ±50 cents: green is inside the tolerance you selected, amber means flat and red means sharp.
5. Change the tolerance if the job needs it. Fine is ±1 ¢, Standard ±3 ¢ (the default) and Casual ±5 ¢.
6. Match your ensemble’s reference pitch. Drag the A4 slider from 415 to 450 Hz, or press a chip (A415, A430, A432, A440, A442, A444). Click a string row to lock onto it instead of Auto-Detect Closest.

What the readout shows

The display reports four values at once: the detected frequency in hertz, the target frequency for the active string, clarity as a percentage, and the cents deviation from the target. The needle is damped so small hand movements do not throw it around, while the detector re-runs every 50 ms so a slow turn of a peg still tracks.

Clarity is the confidence of the periodic match. Live microphone input has to clear 85% before a note is reported; a noisy room or two strings ringing together keeps the readout idle. Frequency comes from the composite waveform rather than a single spectral peak, and sub-sample parabolic interpolation turns that period estimate into a sub-cent frequency.

The presets bound the search window, which stops octave errors: guitar presets listen from about 65 Hz to 800 Hz, bass presets reach down to 25 Hz for B0, and Chromatic spans roughly 25 Hz to 2.2 kHz. Presets whose lowest string sits below 70 Hz use a 4× decimated detector that treats the whole frame as its correlation window, which is how a 30.87 Hz B0 is still tracked on a laptop microphone.

Preset	Strings (low to high)	Target frequencies at A4 = 440 Hz
Guitar (Standard)	E2 · A2 · D3 · G3 · B3 · E4	82.41 · 110.00 · 146.83 · 196.00 · 246.94 · 329.63 Hz
Guitar (Drop D)	D2 · A2 · D3 · G3 · B3 · E4	73.42 · 110.00 · 146.83 · 196.00 · 246.94 · 329.63 Hz
Bass (4-string)	E1 · A1 · D2 · G2	41.20 · 55.00 · 73.42 · 98.00 Hz
Bass (5-string)	B0 · E1 · A1 · D2 · G2	30.87 · 41.20 · 55.00 · 73.42 · 98.00 Hz
Ukulele (Standard C)	G4 · C4 · E4 · A4	392.00 · 261.63 · 329.63 · 440.00 Hz
Violin	G3 · D4 · A4 · E5	196.00 · 293.66 · 440.00 · 659.25 Hz
Viola	C3 · G3 · D4 · A4	130.81 · 196.00 · 293.66 · 440.00 Hz
Cello	C2 · G2 · D3 · A3	65.41 · 98.00 · 146.83 · 220.00 Hz

The ukulele preset keeps its re-entrant high G in the listed position, so the fourth string is higher in pitch than the third. The violin preset adds a Bow drone (root, fifth and octave with slow detune) and notch-filters it out of the microphone path so detection keeps working while it sounds.

Individual pages go deeper: guitar, bass, violin, cello, ukulele, mandolin, banjo, double bass and flute.

Cents, A4 and tuning standards

One semitone is 100 cents, so cents = 1200 × log2(f_detected / f_target). A played 442.5 Hz against a 440 Hz target is +9.8 ¢ sharp. Three cents is a frequency difference of about 0.17%, which is why a reading inside ±3 ¢ counts as in tune for performance work.

ISO 16 fixes the A4 reference at 440 Hz with a tuning accuracy of ±0.5 Hz, and that is the default here. Historical and regional pitches differ: Baroque ensembles often use A415, some European orchestras tune to A442 or A443, and A432 has a following of its own. Set the reference before tuning, because every string target moves with it. The A440 vs A432 vs A442 guide covers the conventions.

Accuracy, limits and troubleshooting

• Low strings need a strong signal. Laptop and phone microphones roll off below roughly 80 Hz, so the fundamental of E1 (41.20 Hz) or B0 (30.87 Hz) can be weak. Play firmly and let the attack settle; the decimated detector reconstructs the fundamental from the overtone spacing.
• One note at a time. The detector locks onto a single repetition rate, so a full chord or two ringing strings will not resolve. Mute everything you are not tuning.
• Clarity gates the readout. If the needle stays idle, the input is below the 85% confidence gate. Move away from fans, air conditioning and mains hum, and play close to the microphone.
• System input processing can change the waveform. macOS Voice Isolation and Windows audio enhancements apply noise suppression or gain that can confuse a pitch detector; switch them off for tuning.
• The microphone stream is released when you stop. Audio is processed in browser memory only, and no sample is stored or transmitted.

Related tools

• Chromatic Tuner — free note detection for any single pitch across the full range.
• Guitar Tuner — standard, drop and open tunings with string-by-string targets.
• Violin Tuner — G3, D4, A4 and E5 with a bow-friendly reference tone.
• Tuning Generator: reference pitches and drones for tuning by ear.