A tuner gives you one number and an arrow. Sing or play a note here and you get its shape: how you scooped into it, what your vibrato is actually doing, which overtones your instrument produces, and whether you held it or drifted. Nothing leaves your browser.
Six seconds of pitch, drawn against the semitone grid. The wobble is vibrato, the slope is drift, the smear at the start is your attack.
Log frequency. The stack of stripes is your harmonic series — that stack is what makes a clarinet sound unlike a voice on the same note.
Strength of each partial, and how far it sits from a whole-number multiple of the fundamental. Real strings run progressively sharp up the ladder.
Hold a note for about half a second and it gets measured. Vibrato depth is corrected for the smoothing of the analysis window.
Cents. A hundredth of a semitone. Trained ears notice about 5 cents on a sustained note, and roughly 10–15 cents in passing.
Confidence. Overtone will not name a note it cannot hear clearly. Below the confidence gate it draws grey and prints nothing, because a tuner that guesses an octave wrong is worse than one that says nothing.
Sway and drift. Sway is how much the pitch moved in total; drift is how far the centre of the note travelled from its first third to its last. Steady vibrato is high sway with near-zero drift. Sagging is the other way round.
Settling. How long after the attack the pitch stayed within 20 cents of where it ended up. Wind and voice usually scoop; a plucked string is nearly instant.
One note at a time. Overtone follows a single voice, so play a chord and it will still show you one number. The maths does find a real pitch — the lowest note whose harmonics all the chord tones sit on, which for a C major triad is a C two octaves below anything you played — but it is a true answer to the wrong question. Trust the reading for one note at a time and treat chords as a curiosity. Overtone does not try to guess which inputs are chords: every test that separated them also mistook quiet fundamentals and hummed low notes for chords, and wrongly refusing a note you really sang is the worse failure.
The cents beside each partial. Ideal harmonics are exact whole-number multiples. Real strings are not: their partials go progressively sharp, which is why piano tuners stretch the octaves. On a piano note you can watch that number climb as you go up the ladder.
Just-intonation lines. Lock a reference note, tick the box, and the ribbon marks where a pure third (−14 cents) and a pure fifth (+2 cents) sit against the tempered grid. Those gaps are why a chord can be perfectly in tune and still sound sour.