The Boss TU-12H Chromatic Tuner features 2 modes, one in a low-frequency band and another in a high-frequency range. Hands-off tuning so you can keep your hands on your instrument. You simply play a note and the Boss TU-12H "knows" what note it is, whether you're sharp or flat, plus it displays how many cents sharp or flat you are. Boss Chromatic Tuner LED lights up when you are on perfect pitch, while sweep meter indicates in cents how close you are.