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So, you’re waiting for your dinner to arrive and you’re bored out of your mind. There’s nothing to read… the conversation is slim to none… and you’ve already counted all of the sugar packets. Hmmm? There’s a straw… and straws are interesting. Is there anything you can do with a straw to “be amazing?” Keep reading – in a matter of minutes you’ll have the entire restaurant upset by your science antics.
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By David Cash PhD
Curriculum Connection: Grade 11 Physics. Cross-curricular Connection: Music, History, Arts
The glass harp and the glass harmonica are musical instruments that produce sound waves in the air from vibrating glass. A glass harp is a set of goblets on a table (see the photographs below). A glass harmonica is a set of rotating glass bowls or bands (see the photographs following below). The glass harmonica instrument was devised and constructed by the American inventor Benjamin Franklin. There is a thread of events connecting the invention of the glass harp in 1742, the invention of the glass harmonica in 1763, and Donizetti composing his opera in 1835. This topic connects the physics of sound, the history of technology, the history of music, and the psychology of popular mythology.
Richard Pockrich and the Glass Harp
The glass harp is a set of glass vessels, typically stemmed goblets, of
varying size, set on a table. When tapped or more usually rubbed with
a finger, a glass goblet vibrates and thus produces sound waves in the
air. Each glass goblet is tuned to a particular pitch by partially filling it
with water. The sound of a glass harp may be described as plaintive,
eerie, or ethereal.
The use of glass by fairground entertainers to produce musical sound
probably dates to the early 1500s, as does the production of glass
goblets.1 The Irish entrepreneur-showman-musician Richard Pockrich
(1695-1759)2 is credited as the first person to present a musical concert in this manner. His first concert took place in Dublin in the year 1744. An earlier attempt in 1742 had been abandoned when the ‘instrument’ was destroyed by an accident just prior to the performance. This musical instrument has come to be known as a glass harp.3
Richard Pockrich and his glass harp is the subject of a 28-minute radio documentary4 produced for Irish Radio 1 (RTE), first broadcast on August 3, 2013, and re-broadcast by CBC Radio 1 overnight on the morning of August 4, 2013.
You can hear and see a glass harp being played by the modern day virtuoso, Robert Tiso, on YouTube.5 Observing the playing of
the instrument, one can appreciate that it is very fragile, and in
addition to musicianship, requires superior reflexes, co-ordination,
agility and endurance in the player.
The physics of the musical glass is described in a report by university student Elaine O’Mara, available for download.6 She found that the maximum sound level is produced midway down the bowl of a glass. The frequency or pitch of a glass is lowered by increasing the size of the bowl, by making the glass of the bowl thicker (more massive), or by filling the bowl with water. O’Mara includes plots of amplitude vs. frequency for four goblets, from which one can see the patterns of harmonics of the glasses. These patterns may be contrasted with similar plots for a flute, a piano string, and a guitar string.7
Glass and Safety
From 40 years of experience in hand-washing fine stemware goblets, I can tell you that glass is very fragile. When glass shatters, the resulting fragments have sharp edges and are very hazardous. The pieces may be small or large, and may be spread over a large area. The clean up is labourious, and you can never be sure you have all the pieces. If you choose to experiment with glass:
1. Do not use stemware. Use thick-walled glass vessels. Tap the vessels like bells, rather than using fingers to rub the rims, or use fingers that you do not need!
2. Lay out a large, heavy plastic sheet to catch all the glass that breaks.
3. Wear safety glasses and be prepared with first-aid supplies.
Questions for Students
1. What substance vibrates to produce sound waves in the air for each of these musical instruments: glockenspiel, violin, xylophone, harp, oboe, brass bell, brass tuba, kettle drum? Can you think of any other substances used to produce vibrations and musical sounds?
2. Search for plots of amplitude vs. frequency for the sound produced by the instruments listed in Question 1, or similar instruments. Compare these plots to those of the glass goblet (Reference 6), a flute, a piano string, and a guitar string (Reference 7). Why is the sound of glass so unusual?
3. The ETF radio documentary ends by remarking that Pockrich was able to live very comfortably in London, as he was able to earn £ 6 for each concert at the time of his death in 1759. How much is that in today’s Canadian dollars? (http://safalra.com/other/historical-uk-inflation-price-conversion/)
Benjamin Franklin and the Glass Harmonica
Pockrich’s glass harp performances and the instrument itself stimulated great interest in Europe. There were many imitators who performed publicly, including the composer Christoph Gluck (1714-1787)8 and Edward Delaval (1729-1814).9 The latter was a scholar and scientist, a fellow of the Royal Society of London (FRS), and the winner of the Royal Society Copley medal in 1766 for his study of metals and glass. In May 1761, the American scientist Benjamin Franklin (FRS) attended a glass harp performance by Delaval in Cambridge, England.10
Benjamin Franklin11 was a person of many great accomplishments. He was a scientist of the first rank, and a creative inventor. I imagine him looking at the table of glasses, tuned with water, being energetically played by Delaval, and thinking: there must be a better way to do this! By 1763, Franklin had worked with glass technologists to conceive and construct what he later called his ‘Armonica’, which is now called the glass harmonica.
Only the bowl of the glass is required to produce sound. Bowls may be
tuned by grinding away glass, to a particular desired note. Franklin then turned the bowls sideways, and nested them concentrically. A hole was drilled in the centre of each bowl, and they were affixed to an iron rod. The rod was turned mechanically by a foot-operated treadle. The player sat in front of the instrument like the player of a harpsichord. Franklin painted his bowl rims in different colours to aid the player.
The glass harmonica is compact, robust, requires no tuning, and requires no great amount of physical prowess to play. Chords are easily played. The instrument became very popular, and was produced in great numbers in Europe, particularly in the German-speaking states. While an excellent instrument for the music room of a house, the glass harmonica was not a suitable instrument for the concert hall. The level of the sound produced is far too low for a large hall. Most composers of the time wrote music for the instrument, including Mozart (1756–1791). You can hear one of Mozart’s compositions played on a modern glass harmonica on YouTube.12
Questions for Students
4. The glass bowls of the harmonica are mounted such that the size of the bowls goes from large to small, left to right. Why left to right?
5. Does a glass harmonica need to be ‘tuned’, as a piano does? How will a temperature and/or a relative humidity change in the room affect the pitch of notes produced by the glass? Explain. (This is a ‘blue-sky’ question.)
6. How does the foot-treadle mechanism convert the up and down motion of the pedal into a rotation of the iron rod in the harmonica? Draw diagrams to illustrate.
The Glass Harmonica and Mental Disturbance
After a period of some decades during which the glass harmonica became very popular, the notion began to take hold that playing the instrument or listening to the sound was injurious to mental health. This idea became very powerful, and it came to be strongly believed that the sound was capable of causing mental disturbance and melancholia. By 1830, its use was strongly discouraged or banned in the German-speaking states of Europe, and production of new
instruments ceased.4, 13
Donizetti’s Opera ‘Lucia Di Lammermoor’
Gaetano Donizetti (1797-1848)14 wrote the opera ‘Lucia di Lammermoor’ in 1835. “The story concerns the emotionally fragile Lucy Ashton (Lucia) who is caught in a feud between her own family and that of the Ravenswoods. The setting is the Lammermuir Hills of Scotland (Lammermoor) in the 17th century.” Forced to marry by her family after the murder of her lover, she commits murder-suicide in what is known as ‘the mad scene’ at the end of the opera.15
Donizetti originally scored some of the scene for glass harmonica because of its reputation and sound, but a dispute with the musician forced him to rescore the part for flutes. Only since the modern production of the glass harmonica instrument has it been possible to restore the original scoring and utilize a glass harmonica in productions, such as the Canadian Opera Company production in Toronto in 2013.16, 17
The Modern Glass Harmonica
Construction of modern glass harmonicas began about 30 years ago.18 There are now a number of artists performing on the instrument.19
1 Corning Museum of Glass: http://timeline.cmog.org
Oxford Journals: http://jdh.oxfordjournals.org/content/26/2/133.short
2 Richard Pockrich: http://en.wikipedia.org/wiki/Richard_Pockrich_(inventor) ;
3 Glass Harp: http://en.wikipedia.org/wiki/Glass_harp
6 Elaine O’Mara Physics Report: http://courses.physics.illinois.edu/phys193/Student_Reports/Fall08/
9 Edward Delaval: http://en.wikipedia.org/wiki/Edward_Hussey_Delaval
10 History of the Glass Harmonica: http://www.glassarmonica.com/index.php ;
11 Benjamin Franklin: http://www.fi.edu/learn/sci-tech/armonica/armonica.php?cts=benfranklin-recreation
12 Wolfgang Amadeus Mozart: http://en.wikipedia.org/wiki/Wolfgang_Amadeus_Mozart ;
13 Benjamin Franklin’s Madness Inducing Machine: http://outofthiscentury.wordpress.com/2010/02/10/benjamin-franklins-madness-inducing-machine/
14 Gaetano Donizetti: http://en.wikipedia.org/wiki/Gaetano_Donizetti
16 New York Times 2007 10 05: http://www.nytimes.com/2007/10/05/arts/music/05glas.html?_r=0&adxnnl=
17 Canadian Opera Company Program, Spring 2013 (Pages 22 and 24):
18 Gerhard Finkenbeiner: http://finkenbeiner.com/GLASSHARMONICA.htm
19 Glass Harmonica Performance: https://www.youtube.com/watch?v=eQemvyyJ—g
[Milan – plse. do footnotes. I can’t make them small. Do you want me to identify where they are? There are 19 of them. Volume 45 • 3 February 2014 Crucible. ]
David Cash is a retired Mohawk College professor. He may be reached directly at: email@example.com.
After sight, hearing is the most important of our five senses. Sound is caused by waves, and sounds are made by vibrating objects. Sounds can vary in two ways: amplitude and pitch. The amplitude of a wave tells us how much energy was used to produce it. The greater the amplitude, the greater the volume. Frequency is the number of waves or vibrations sent out in a specified amount of time; the faster something vibrates, the higher the pitch.