APP with auto noise filtering. First step is choose the frequency at top of screen, then choose the tuning at the middle of the screen. When you play instrument, the pitch will be shown on the panel for the individual string by indicating signal high or low. [Tuner] - Calibrate Piano Sound : Click on an string then calibrate the sound with your instrument. Piano Sound A4=442. - A4 Frequency adjustment: choose 428~452 frequencies for A4 string. - The scale for precision tuning is 10 Quantile