Aeolian harps, named after the Greek god of wind, Aeolus, are designed to produce sounds as the wind passes through them. A wooden box, two bridges, and a set of strings that stretch over the bridges along the length of the harp were the only essential components of traditional aeolian harps. To achieve desired pitches, aeolian harp strings can be made from a variety of materials and thicknesses.
The aeolian harp, a popular Romantic Era household instrument, can still be found in modern homes all over the world. Many aeolian harps are handcrafted by skilled artisans, while others are mass-produced by machines. They come in a variety of sizes and can be made of a variety of materials, including steel and aluminum. Almost any type of wood can be used to make one of these harps.
Smaller versions of these harps are usually placed in open windows, where wind can blow over their strings and produce sounds. Large aeolian harps can be permanently installed atop a building or on a windy hilltop and are made of hard steel or a durable wood species like oak. Large aeolian harps are featured prominently in many monuments and public art installations.
Aeolian harps work by harnessing a phenomenon known as “vortex street,” which causes spiral eddies of fluid or air known as von Karman vortices to form. In the oceans and the atmosphere, Von Karman vortices, which travel in linear chains, are fairly common. In the presence of wind, the vortex motion that activates an aeolian harp is the same motion that causes a flag to ripple left and right. Wind blowing across the strings of an aeolian harp causes the strings to vibrate, producing sound.
Aeolian harps can produce a wide range of sounds, from low, almost imperceptible hums to extremely loud tones. The tone of an aeolian harp is greatly influenced by the strength of a wind gust. The strings of an aeolian harp, however, will only produce the tones or frequencies at which each string naturally resonates, regardless of how strong the wind is; the wind can only enhance a string’s natural tone.
Aeolian harp strings that are lightweight, tight, and shorter produce higher tones, while heavier, loose, and longer strings produce lower tones. Strings on an aeolian harp with a smaller diameter produce higher tones, while strings with a larger diameter produce lower tones. In the right wind conditions, the right string combination can produce a specific chord.