Reference tone
Short beep or sustained drone for tuning by ear, with one-click A440. Default A4 = 440 Hz.
Choose a note
Click a note for a quick preview, or start a drone for a sustained tone to tune against.
Pick a note, then press Play, Drone, or A440.
Illustrated reference
A pitch reference and a time reference

Metronome: A click marks time; it does not tell you the note pitch. Set: Choose a comfortable tempo and meter. Count: Match the beat before adding notes. Build: Increase speed only while the pattern stays clear.
Reference tone: A4 = 440 Hz is the standard reference used here. Choose: Select the note and octave you need. Listen: Compare one open string with the reference. Match: Use the tuner and your ear to confirm pitch.