Fourier analysis · live

Fourier Tuner

Autocorrelation finds the period, the FFT shows the harmonics. Everything the detector sees is on screen.

Pitch readout

no stable pitch

flat
—
sharp
-50¢listening…+50¢

Time domain · oscilloscope

zero-cross triggered, period locked

Frequency domain · FFT magnitude

4096-point, 0–4 kHz

Metronome

500.0 ms / beat · 2.000 Hz

120
bpmAllegro

4/4 · accent on beat 1

Under the hood

Fundamental f₀—Hz
Target note—
Target freq—Hz
Deviation—cents
Period—samples
ACF clarity—%
Level (RMS)—
Spectral peak—Hz
Peak bin—
Sample rate48,000Hz
Bin width11.72Hz
MIDI note—

How it works

  1. 01Mic audio is captured raw — no AGC, no noise suppression — into a 4096-sample window.
  2. 02The FFT decomposes that window into frequency bins: the spectrum panel is Fourier's view of your sound.
  3. 03Autocorrelation (the FFT's time-domain twin) finds the lag where the wave repeats — that lag is the period.
  4. 04Parabolic interpolation refines the peak, giving sub-bin frequency precision.
  5. 05Frequency becomes a note via 1200·log₂(f/f_target) cents against your A4 reference.