Pitch Detector

About this tool

Sing, hum, or play a single sustained note and this shows the nearest musical note, its exact frequency in Hz, and how many cents sharp or flat you are — a chromatic tuner that works for voice or any instrument, tuned to standard concert pitch (A4 = 440 Hz). Audio is analyzed locally in your browser using the Web Audio API; nothing is recorded, uploaded, or saved.

How it detects pitch. The raw waveform is analyzed with autocorrelation — it compares the signal against time-shifted copies of itself to find the shift where they line up best, which is the fundamental period of the note. That period converts directly to a frequency, and parabolic interpolation between samples sharpens the estimate beyond what the raw sample rate alone would give.

Reading the needle. The bar runs −50 to +50 cents (a cent is 1/100th of a semitone) with the nearest note centered at 0. Green from −5 to +5 cents is close enough that most ears can't tell the difference; amber out to ±20 cents is noticeably off; red beyond that is a different note away from being in tune.

What it needs to work well. One clear, sustained pitch at a time — a single note, a hum, a sung vowel. Chords, percussion, and rapid vibrato don't have one fundamental frequency to lock onto, so the reading holds its last value or shows "no clear pitch" rather than guessing. It covers everything from a low guitar string up through a high vocal note comfortably; well below that (deep into bass-guitar or organ-pedal range) there often isn't enough of a full wave cycle in each analysis window to detect anything at all, so it stays blank rather than showing a wrong note.

Frequently asked questions

Can I tune to something other than A440?

Not yet — this reads pitch against standard concert pitch (A4 = 440 Hz), the tuning almost all modern instruments and orchestras use. Alternate tunings like A432 or a baroque A415 would shift every note name by a fixed offset from what's shown here.

Why does the reading jump between two different notes?

That usually means the true pitch sits almost exactly between two notes (near ±50 cents), so small variations in your voice or instrument tip the nearest-note calculation one way or the other. Small vibrato, background noise, or a signal that's too quiet can cause the same flicker.

Is my audio recorded or sent anywhere?

No. The microphone stream is read locally for the live analysis only — it's never recorded, saved, or transmitted, and access stops the moment you click Stop or leave the page.

Why does a low note sometimes read an octave off?

Autocorrelation can occasionally lock onto a sub-harmonic (half the true frequency) on a noisy or very low-pitched signal, since two full waveform cycles can look almost as well-aligned as one. Playing a touch louder and closer to the microphone usually clears it up.

Does this work with instruments, or just voice?

Both — it detects the fundamental frequency of whatever single sustained pitch the microphone picks up, whether that's a sung note, a plucked string left to ring, a wind instrument, or a tone from another app or device.