A harp is basically a large wooden triangle, usually made primarily of maple. The front, vertical side of the triangle is known as the column or the forepillar. The upper, curved side of the triangle is known as the neck. The third side of the triangle is known as the body. White maple is the best wood for these three sides because it is strong enough to withstand the stress of the strings. The soundboard, which is contained within the body and which amplifies the sound of the strings, is usually made of spruce. Spruce is used because it is light, strong, pliable, and evenly-grained, enabling it to respond uniformly to the vibrations of the strings to produce a rich, clear sound. The middle of the soundboard, known as the centerstrip, is attached to the base of the strings and is usually made of beech. Beech is used because it is tough enough to bear the tension of the strings.
The curved plate on the neck of the harp, to which the strings are attached, is made of brass. The disks which control the length of the strings are also brass, as are the pedals which control the disks. These external metal parts are often plated with gold for appearance and to resist tarnishing. The complex internal mechanism which connects the pedals to the disks, known as the action, is made of brass and stainless steel, with some parts such as washers made of a hard plastic such as nylon.
The strings of a harp are made of a variety of materials, including steel, gut (derived from the intestines of sheep), and nylon. Each material has different properties which make it suitable for a particular length of string.
The surface of a harp may be treated with clear lacquers or wood stains of various colors such as ebony or mahogany. It may also be inlaid with decorative woods such as walnut or avodire (a pale yellow West African wood). Some harps are gilded with 23 karat gold leaf. The soundboard may be decorated with paint or gold decals.