Beating two frequencies against each other and being able to see visually when the beat frequency goes to zero is one of the most precise ways to match two frequencies. A related idea is the use of Lissajous patterns on an oscilloscope, but this tuner uses a strobe technique in which a flashing pattern becomes stationary when two frequencies match. Not only is this tuner accurate, but it also makes tuning fast. My previous method of tuning made use of harmonics and listening for beat frequencies after I set a 440 A note. The method is accurate provided one can hear the beat frequencies in the presence of background noise, however it also takes a lot of time to get the tuning right. With this visual strobe tuner, however, background noise is no longer an issue, and I can tune more quickly just by watching for when the rotating strobe pattern becomes stationary. It also works with my previous use of harmonics, but now I can see rather than hear when the beat frequencies go to zero. This tuner also provides access to what Peterson calls "Sweet Tunings" in which compensation can be made for string tension, guitar action, and the inaccuracies of the equal tempered scale. It makes adjusting the guitar for the best sound in various keys speedy and accurate. The tuner is very compact and folds up to fit easily in the guitar case. I would recommend getting the little protective case so that the tuner doesn't accidently get turned on when mashed against other things in the guitar case. Also, get the USB cable and go online to the Peterson site and download the latest firmware update when registering the tuner. This tuner easily gets five stars from me.