what is rosin for
A cake of rosin, made for use by violinists, used here for soldering. Rosin, also called colophony or Greek pitch (Pix graeca), grÃ¦ca 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 Rosin is often applied to the bow before playing the instrument. 2  Lighter rosin is used for violins and violas. 3  There are darker rosins for cellos and specific, distinguishing types for bassesâfor more see Bow (music) .