The Guitar is a string instrument. Guitars typically have six strings, but eight, ten, twelve and eighteen string guitars also exist. The Guitar has been the most popular and widely-known of musical instruments since the second half of the 20th century, as it is used in a plethora of popular musical styles, such as jazz, blues, rock and pop. Nevertheless, the guitar also has a long history within the context of classical, “academic” music, as the protagonist in many national musical idioms, and as a solo instrument. In Greece, the Guitar appears in many different music genres, contemporary as well as traditional, such as rebetika and folk music, often as accompaniment. The Guitar consists of two parts, the body and the neck. The bridge, which holds the strings in place, is fixed onto the body. The strings are then tightened over the Guitar, and fixed on the tuners (machine heads) on the headstock. The neck is the long, narrow part that houses the fretboard, the truss rod and the tuners, which are fitted with capstans for adjusting the tension of the strings and thereby tuning them. The neck on classical guitars is attached to the body, while in other types (primarily electric guitars) it is often detachable. The frets, which determine the scale length, are embedded along the fretboard, on the neck.