In music, a bow is a tensioned stick which has hair coated in rosin affixed to it. It is moved across some part of a musical instrument to cause vibration, which the instrument emits as sound. The vast majority of bows are used with string instruments, such as the violin, viola, cello, and bass, although some bows are used with musical saws and other bowed idiophones.
Frog of a modern violin bow (K. Gerhard Penzel)
Tip of a modern violin bow (K. Gerhard Penzel)
Turning the screw on a modern violin bow causes the frog (heel) to move, which adjusts the tension on the hair.
Rosin, also called colophony or Greek pitch, is a solid form of resin obtained from pines and some other plants, mostly conifers, produced by heating fresh liquid resin to vaporize the volatile liquid terpene components. It is semi-transparent and varies in color from yellow to black. At room temperature rosin is brittle, but it melts at stove-top temperature. It chiefly consists of various resin acids, especially abietic acid. The term colophony comes from colophonia resina, Latin for "resin from Colophon", an ancient Ionic city. It is an FDA approved food additive.
A cake of rosin, made for use by violinists.
Pharmaceutical rosin
An etching plate covered with powder resin
Various types of rosin for violins, violas and cellos