This small device tunes by sensing vibrations from the instrument, which are picked up by a built-in piezo transducer. The CHT worked great on a recent gig in a noisy room. Attached to the headstock of a Joe Veillette Jazz 14 guitar, it provided clear sharp/flat indications that made it easy to tune quickly and accurately between songs. I also really like how the how the display switches from red to green when you're up to pitch. This a cool product!