This chapter begins with a discussion of the importance of separate thinking about each movement in practicing and playing a string instrument. The sound post is a dowel, which fits vertically between the front and back of the instrument. The sound post is generally positioned slightly to the bottom and right of the edge of the bridge, the exact placement being determined by the position that produces the best tone quality. Most student-line bows consist of a stick made of fiberglass, graphite, or a composite material, and synthetic hair. Higher-quality bows are made of pernambuco, rosewood, or brazilwood with the hair from a horse mane or tail. The bow hair is tightened or loosened by holding the frog with the left hand and turning the bow screw with the right. The purpose of the shaped body of a string instrument is to ensure that the air inside has a large number of resonant frequencies.