It listens to you and tells you the truth about the note.
The microphone is off. Nothing is being recorded or sent anywhere — the sound never leaves this computer.
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flat (under)in tunesharp (over)
Listen mode.
Turn the microphone on.
Hum with your lips closed, any comfortable sound, and hold it.
The big letter is the note you are making. The bar shows where you are sitting between two notes, and the word under it says whether you are holding the pitch still.
Nothing to pass or fail here. This is you meeting your own voice on a screen.
Match mode. Press play, listen, then sing the same note on "ah".
In tune means within 10 cents. A cent is one hundredth of a half-step — 100 cents is the gap between two neighboring piano keys.
Find my range. The bench plays a note, you sing it back on "ah" and hold it. It walks down until you run out of low notes, then up until you run out of high ones.