In music, a note's pitch is its frequency, measured in hertz (Hz). A person who listens to a note can recognize its pitch.

This app makes it possible to check the pitch of a sound you record with your smartphone or tablet's microphone. It also displays a graph of the sound, which makes it easy to see what it sounds like.

A note's pitch varies over a wide range of frequencies, from approximately 220 Hz to more than 20 KHz. It is important to be able to differentiate between tones, even between those that are quite close together, because the human ear is very sensitive to slight differences in frequency.