What it does
A musical note is a mix of a fundamental and its overtones. How strong each overtone is gives an instrument its colour, and how far the overtones sit from exact whole-number multiples tells you about the string, pipe or bar that made them. This analyser takes one note and shows:
- the spectrum (level in dB against frequency), averaged over overlapping frames with the window you choose;
- the fundamental frequency, the nearest note and how many cents it is off 12-tone equal temperament (A4 = 440 Hz);
- each harmonic: its measured frequency, how many cents it sits above or below n × f₀, and its level in dB, also relative to the strongest;
- the inharmonicity coefficient B from fₙ = n f₀ √(1 + B n²): near 0 for winds and bowed strings, clearly above 0 for pianos, guitars and bells;
- the spectral centroid, the amplitude-weighted mean frequency, a common measure of brightness, also as a multiple of f₀.
How to use it
- Press Open an audio file and pick a recording of one sustained note (WAV, MP3, OGG, FLAC or M4A). Or press Record from the microphone: your browser asks first, the recording lasts the time you choose, and it stays in the page’s memory only. If the microphone is blocked, record with another app and open the file.
- Set Analyse from and Length to a steady part of the note, after the attack.
- Choose the FFT size and window. Hann is a good default; Blackman shows weak partials next to strong ones better; a longer FFT separates partials that are close together.
- If the pitch is found an octave off, type the fundamental yourself.
Worked example
Press Use the example: the page makes a stiff-string tone at 110 Hz with 24 partials stretched by B = 0.0003. Analysing 1 s from 0.1 s with a 16,384-point Hann window (4 frames averaged, 2.69 Hz per bin), it reports Fundamental 109.99 Hz (A2 −0.1 ¢), inharmonicity B = 3.01 × 10⁻⁴ and 16 of 16 harmonics found. The partials run progressively sharp: the 2nd harmonic is 0.9 cents above 2 × f₀, the 8th 16.6 cents, the 16th 64.2 cents, exactly the stretching a piano tuner meets. The 2nd harmonic is 7.2 dB below the fundamental and the 16th 28.6 dB below.
Tips
- Record close to the instrument in a quiet room, without clipping. The page warns if the analysed part reaches full scale.
- Compare instruments or playing styles with the same settings and segment length.
- The spectrum CSV has every bin, for your own plots; the harmonics CSV has the table.
FAQ
Why is the fundamental an octave off? Some sounds have a weak or missing fundamental, or very strong even harmonics. The page uses all the harmonics to decide, but you can type the fundamental to override it.
Is my recording kept or uploaded? No. The file or recording is decoded in your browser, held only while the page is open, and never sent anywhere.
Where the numbers come from
- Discrete Fourier transform with Hann, Hamming, Blackman or rectangular windows and frame averaging (Welch), parabolic interpolation of spectral peaks, the stiff-string partial formula fₙ = n f₀ √(1 + B n²) (Fletcher), and the spectral centroid: standard signal processing and musical acoustics.
- Checked against NumPy (rfft) and SciPy windows on a synthetic tone with stretched partials and noise: spectrum values to 10⁻¹², the five strongest peak frequencies and levels to 10⁻⁹ and the centroid to 10⁻⁸; f₀ and B recovered from tones of known f₀ (41 to 1047 Hz) and B.
- The example tone is synthesised by the page; it is not a recording.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-09.