There are also really high-end tuners, and one of the most impressive is called a polyphonic tuner. Most guitar tuners have you tune one string at a time, adjusting the tension and then moving on to the next string. Polyphonic tuners allow you to strum all the strings at once, fully open (with no hand on the strings), and it’ll tell you at once which string to tune, if any. That also makes it ideal for alternate, non-standard tunings, which are often pre-loaded. Just plug, strum and tune. It’s much faster (and leagues cooler) than other tuners.