Aeolian harp

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Aeolian harp in the old castle of Baden Baden, from an article in Scientific American Supplement, No. 483, April 4, 1885

Another aeolian harp

An aeolian harp (or æolian harp or wind harp) is a musical instrument that is "played" by the wind. It is named for Aeolus, the ancient Greek god of the wind.

German scholar and a renowned Egyptologist, Athanasius Kircher (1601–1680) is credited with having constructed the first Aeolian harp in 1650.

History

The Aeolian Harp, also know as Harmonic Harp, originated in ancient Greece and achieved great popularity in Europe during the Renaissance. Aeolian harps were very popular as household instruments during the Romantic Era, and are still hand-crafted today. Some are now made in the form of monumental metal sound sculptures located on the roof of a building or a windy hilltop.

Aeolus was the Greek god of the winds and ruler of the island of Aeolia. In Homer's Odyssey, Aeolus provides the wandering Odysseus favorable winds to aid him on his journey.

The Aeolian harp is a Greek invention, played by the winds. It has a dozen or so strings, all the same length — about five feet. Each has a different diameter, but they're all tensioned to the same unison pitch. Years ago, when I taught at Washington State University on the windblown steppe of western Washington, I had a contract with the Bonneville Power Company. My task was to study Aeolian vibration as it occurred, not in a harp, but in their power lines.

In a gentle wind, a power line will sing, just as a catgut or nylon string will sing in an Aeolian harp. That vibration can, eventually, cause the wire to fatigue and break. In a severe wind, or when ice forms an airfoil shape around the wire, it can gallop wildly and cause severe damage. Vast human ingenuity has gone into the problem of damping out vibration to protect the wire.

So imagine wind passing over any cylinder: The air has to speed up to get around it. A fast-moving stream separates from the cylinder and whooshes away behind it. That creates a low-pressure region just behind the cylinder. The two sheets of fast-moving air both want to collapse into the space behind the cylinder, but they do so alternately, in a rhythm that depends on the size of the cylinder and the airspeed.

That rhythmic collapse is what makes wires sing. You can calculate its pitch in cycles per second, or hertz. It comes to about one fifth of the airspeed divided by the diameter.

You can also feel the Aeolian sound. Next time a breeze is blowing at, say, twenty feet per second, stand a few feet behind a one-foot-diameter telephone pole. Wet your finger, put it in the wake, and you'll feel a four-cycle-per-second flutter. A power cable, a fifteenth of a foot in diameter, gives a sixty-hertz hum. In that same breeze, a gut string, one two-hundredth of a foot in diameter, will sound the note A from a woman's mid-voice range.

The Aeolian harp came back to our modern world when Renaissance scientist Athanasius Kircher recreated it. By 1800, it'd entered the Romantic imagination. Coleridge worked for years on his poem The Aeolian Harp. And, in one version, he says: Methinks, it should have been impossible Not to love all things in a World like this, Where e'en the Breezes of the simple Air Possess the power and Spirit of Melody!

Description

Aeolian harps can vary in terms of their basic design. The traditional aeolian harp is essentially a wooden box including a sounding board, with 10 or 12 strings stretched lengthwise across two bridges. It is placed in a slightly opened window where the wind can blow across the strings to produce sounds. The strings can be made of different materials (or thicknesses) and all be tuned to the same note, or identical strings can be tuned to different notes. There are also larger harps that stand upright in order to catch the wind.

Sound and Operation

The sound is random, depending on the strength of the wind passing over the strings, and can range from a barely audible hum to a loud scream. If the strings are tuned to different notes, sometimes only one tone is heard and sometimes chords.

The general of the instrument's sound production is based on wind producing pitches of the overtone series (Harmonics). According the principles of acoustics, a harmonic is a barely-audible higher pitch contained within a musical tone. The presence of these faint pitches are what produces the tonal characteristics of a particular musical instrument. As wind crosses the strings of the Aeolian Harp it sets the strings in motion (vibrations) and the results is a series of tones (harmonics) most commonly the third, the twelfth, the upper octave intoning over a fundamental unison drone.

The harp is driven by an aeroelastic effect. The merest motion of the wind across a string forces the air on the leading side to move faster than that on the trailing side; then (see Bernoulli's principle) the pressure ahead is slightly less than that behind, pushing the string further to the side, until the restoring force arising from deflection halts and reverses the motion.

The effect can sometimes be observed in overhead utility lines, fast enough to be heard or slow enough to be seen. A stiff rod will perform; a non-telescoping automobile radio antenna can be a dramatic exhibitor. And of course the effect can happen in other media; in the anchor line of a ship in a river, for example.

Aeolian harps in literature and music

Henry Cowell's Aeolian Harp (1923) was one of the first piano pieces ever to feature extended techniques on the piano which included plucking and sweeping the pianist's hands directly across the strings of the piano. The Etude in A flat major for piano (1836) by Frédéric Chopin (Op. 25, no. 1) is sometimes called the "Aeolian Harp" etude, a nickname given it by Robert Schumann. The piece features a delicate, tender, and flowing melody in the fifth finger of the pianist's right hand, over a background of rapid pedaled arpeggios. One of Sergei Lyapunov's 12 études d'exécution transcendante, Op.11 No.9, is named by the author "Harpes éoliennes" (aeolian harps). In this virtuoso piece, written between 1897 and 1905, the tremolo accompaniment seems to imitate the sounding of the instrument.

In 1972, Chuck Hancock and Harry Bee recorded a giant Aeolian harp reportedly built by the members of a commune on a hilltop in California. United released their double LP entitled The Wind Harp - Song From The Hill. In the spirit of this, in 2003 an Aeolian harp was constructed at Burning Man. Australian artist, composer and sound sculptor Alan Lamb has created and recorded several very large scale aeolian harps.

In 2006, Italian New Age composer, Oreobambo, used the Aeolian Harp on his CD Energy Journeys.

English Romantic poet and philosopher, Samuel Taylor Colridge (1772-1834), immortalized the instrument in his poem of 1822 The Eolian Harp, in which he references the harp and wind as being single aspects of the the same universe and origin coming together in a harmonious fashion.

The Eolian Harp (excerpt):

And that simplest Lute,
Plac'd length-ways in the clasping casement, hark !
How by the desultory breeze caress'd,
Like some coy maid half-yielding to her lover,
It pours such sweet upbraiding, as must needs
Tempt to repeat the wrong ! And now, its strings
Boldlier swept, the long sequacious notes
Over delicious surges sink and rise,
Such a soft floating witchery of sound
As twilight Elfins make, when they at eve
Voyage on gentle gales from Faery-Land,
Where Melodies round honey-dropping flowers,
Footless and wild, like birds of Paradise,
Nor pause, nor perch, hovering on untam'd wing !

References

ISBN links support NWE through referral fees

• Bonner, Stephen, Aeolian harp, Cambridge: Bois de Boulogne, 1968. ISBN 0-900-99800-8
• Hankins, Thomas L.; Silverman, Robert J., Instruments and the imagination, Princeton, NJ: Princeton University Press, 1995. ISBN 0-691-02997-0
• Mansfield, Jonathan, The design and construction of an Aeolian harp, Cambridge: Bois de Boulogne, 1970. ISBN 0-900-99810-5

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