For guitar players, bassists and players of pretty much any stringed instrument, tuners are just a fact of life. Off the top of our heads, the only stringed instrument without tuners that we can think of is a tea-chest bass. Some players express strong tuner preferences based on functionality, weight and appearance. Among vintage guitar collectors, a changed set of tuners can be a dealbreaker, Schallers on a vintage Gibson being a particular bête noire for some.
It’s pretty clear what tuners do. On instruments such as guitar and bass, the strings are stretched between two fixed points and the tuner sets the pitch of the open string by applying tension. Increasing this tension raises the pitch; decreasing it lowers the pitch. Friction pegs are still used throughout the violin family and are one of the features that differentiate traditional flamenco guitars from ‘classical’ guitars. This is why some still use the archaic term ‘peg head’, rather than ‘headstock’.