""Guitar tuner"" redirects here, but can also refer to the string tension adjusters also called machine heads. For the radio receiver component, see Tuner (radio)In music, an electronic tuner is a device that detects and displays the pitch of musical notes. Simple tuners indicate—typically with a needle-dial, LED, or LCD display—whether a pitch is lower, higher, or equal to the desired pitch. Software applications can turn a smartphone, tablet, or personal computer into a tuner. More complex and expensive tuners indicate pitch more precisely.Tuners vary in size from units that fit in a pocket to 19"" rack-mount units. Instrument technicians, piano tuners, and luthiers typically use more accurate tuners.The simplest tuners detect and display tuning only for a single pitch—often ""A"" or ""E""—or for a small number of pitches, such as the six used in the standard tuning of a guitar (E,A,D,G,B,E). More complex tuners offer chromatic tuning for all 12 pitches of the equally tempered octave. Some electronic tuners offer additional features, such as pitch calibration, temperament options, the sounding of a desired pitch through an amplifier plus speaker, and adjustable ""read-time"" settings that affect how long the tuner takes to measure the pitch of the note.Among the most accurate tuning devices, strobe tuners work differently than electronic tuners. They are stroboscopes that flicker a light at the same frequency as the note. The light shines on a wheel that spins at a precise speed. The interaction of the light and regularly-spaced marks on the wheel creates a stroboscopic effect that makes the marks for a particular pitch appear to stand still when the pitch is in tune. These can tune instruments and audio devices more accurately than most non-strobe tuners. However, mechanical strobe units are expensive, and their moving parts require periodic servicing, so they are used mainly in applications that require higher precision.