A headstock or peghead is part of a guitar or similar stringed instrument such as a lute, mandolin, banjo, ukulele and others of the lute lineage. The main function of a headstock is to house the pegs or mechanism that holds the strings at the "head" of the instrument. At the "tail" of the instrument the strings are usually held by a tailpiece or bridge. Machine heads on the headstock are commonly used to tune the instrument by adjusting the tension of strings and, consequentially, the pitch of sound they produce.
Two traditional layouts of tuners are called "3+3" (3 top tuners and 3 bottom ones) and "6 in line" tuners, though many other combinations are known, especially for bass guitars and non-6-string guitars. When there are no machine heads (i.e. tuners are not needed or located in some other place, for example, on guitar body), the guitar headstock may be missing completely, as in Steinberger guitar or some Chapman stick models.
The headstock may be carved separately and glued to neck using some sort of joint (such as a scarf joint). There are two major trends in headstock construction, based on how the string will go after passing the nut. The advantages and disadvantages of both trends are very debatable and subjective, so these two variants are used:
Luthiers of both styles frequently cite better sound, longer sustain and strings staying in tune longer as advantages of each style. Fragile construction is cited as a disadvantage of each style too: single-piece necks are more likely to break on occasional hit and are harder to repair, while glued-in necks can break with time.
Apart from its main function, the headstock is an important decorative detail of a guitar. It is the place where overwhelming majority of guitar manufacturers draw their logo. Some guitars without machine heads (for example, ones equipped with Floyd Rose SpeedLoader) have a headstock for purely decorative reasons.
Most major guitar brands have signature headstock designs that make their guitars or guitar series easily recognizable. As seen in a section below, even "copied" at the first glance designs retain clear visible changes in dimensions, proportions of elements, etc., so it is almost always possible to tell a major brand of a guitar by looking at headstock.
Gibson Firebird series (also used in reverse)
Washburn N-series (reverse)
Floyd Rose SpeedLoader Guitars decorative headstock, no machine heads at all
Gibson, used on most of their acoustic and electric guitars since the 1930s, and many before that.
PRS asymmetric, used on most guitars
PRS symmetric, used on Santana 3 model
Gibson Flying V, 1958 issue
ESP "pointed" headstock, used on Horizon NT-II and M-II guitars, as well as many signature models (also used in reverse)
Ibanez "pointed" Ibanez signature headstock, used on most rock-series solid-body electric guitars (also used in reverse)
Jackson "pointed" headstock, used on almost all solid-body electric guitar series (also used in reverse)
Washburn "pointed" headstock, used on almost all rocker-series electric guitars (also used in reverse)
On some electric guitars and basses the finish used on the body is also applied to the face of the headstock. Generally, matched-headstock models carry a price premium over their plain counterparts due to the extra processes involved in the finishing process.
The definition of a "matched headstock" varies between manufacturers and players - for example, the headstocks of Gibson guitars are nearly always black, and it is debatable whether a black-bodied Gibson has a matching headstock. Generally, a guitar is only considered to have a matching headstock if the guitar is usually produced without matching body and headstock finishes.