How does a violin make sound?

A violin has four strings tuned to the notes G, D, A and E. The bow is strung with horsehair coated in sticky rosin, which grips the string, pulls it sideways, then lets it slip back, many hundreds of times a second, keeping it vibrating continuously. The strings rest on a wooden bridge that transmits the vibrations to the violin's top plate, usually made of spruce. Inside, a small wooden rod called the sound post links the top and back, and the f-shaped holes help the sound escape. The player changes the pitch by pressing strings against the fingerboard, shortening the length that vibrates.