GLASS MUSIC WORLD WINTER 2004 1 WINTER 2004 Acoustics of Glass Musical Paris Festival ‘05 Instruments – Program and Information – – by Thomas D. Rossing – Physics Department, Northern Illinois University Ten years have passed since I pub- lished a paper entitled “Acoustics of the glass harmonica” in the Journal of the Acoustical Society of America [1]. That paper discussed the physics of the instrument we all love so well. It was reprinted in the Summer/Fall and Winter/Holidays issues of Glass Music World, and, judging from the feedback I received, fairly well received by readers of that publication. Many performing musicians have discovered that under- standing the physics of their musical instrument (whether it is a violin or an armonica) is a great help in improving their playing technique as well as devel- oping “new sounds” in their instrument. The museum in Cité de la Musique Performers, as well as scientists, love to experiment, and science can profitably Thomas Bloch is now complet- will be on tour in Sydney, Australia for guide their experiments. ing his planning and organizing of the most of the month of January. More recently I wrote a book on Glass Music Festival to be held in and For the festival details as of 12/16, the Science of Percussion Instruments around Paris in early February. He is please see: (World Scientific, 2000) which includes now working out the final details and FESTIVAL, page 4-5 a chapter on Glass Music Instruments [2]. A few GMI members have com- monica and other types of glass musical It is very useful to describe vibrating mented on this chapter, and I would instruments. systems in terms of normal modes of welcome comments from others. In the vibration. A normal mode describes the past ten years, there have been a few Vibrational modes of a wineglass shape of a vibrating system at one of its published reports on scientific research natural frequencies. In a violin string, on glass musical instruments but not In musical instruments, sound is the normal modes describe the back and as many as might have been expected. produced by one or more vibrating sys- forth motion of the string in one or more Most of them have dealt with tuning of tems, such as the vibrating string and segments separated by nodes or points wine glasses, shatter at high amplitude, soundboard of a violin, the vibrating at which the motion is minimal (unfor- glass versions of traditional wind and air column of a trumpet, or the vibrat- tunately, the terms nodes and modes percussion instruments, and novel glass ing membrane of a drum. A discussion sometimes get confused). In the funda- instruments. of vibrating systems found in musical mental mode, the entire string moves in In this article, written for both per- instruments is included in my textbook one direction; in the second mode there formers and experimenters, we will Science of Sound, written especially for is a node at the center and the two halves review the science of the glass har- musicians. see ACOUSTICS, page 2 website: http://www.glassmusicintl.org • egroup: http://groups.yahoo.com/group/glassmusic/ 2 WINTER 2004 GLASS MUSIC WORLD GLASS MUSIC WORLD WINTER 2004 3 move in opposite that one mode in the doublet pair has anodes where the — ACOUSTICS from page 1 — directions. In a other mode has maximum vibration. This behavior is often vibrating string, the modes are very nearly harmonic (that is observed in bells and other systems with circular symme- PRESIDENTIAL their frequencies are multiples of the fundamental frequency). try. The normal modes of a two-dimensional plate or a three- The holographic interferograms in Fig. 3 were made with NOTES dimensional shell are more complicated than those of a one- our electronic TV holography system, which is a rapid and By the time you receive this newsletter, the Paris for this particular festival. Registration fees were charged dimensional string. Fortunately, only the lowest couple of accurate tool for determining modes of vibration in musical Festival will be less than a month away. Thomas Bloch for both the 1997 and 2000 festivals. In the future, we will modes of a wineglass are of musical importance, and these instruments (considerably faster than recording them on has done an outstanding job of planning and organizing undoubtedly have to go back to charging registration fees for are relatively simple. The first three modes are shown in Fig. photographic film as in Ref. 1). this festival and at times it has been very difficult for him. festivals, especially if we have them more frequently. Three 1, which is reproduced from my earlier article in GMW. The You may recall that after he had made arrangements for members have corresponded with me about their desire to nodes appear in white, and the fringes provide a contour map Sound of armonica and glass harp the festival with the Director of the Cite de la Musique, have festivals in their communities in the future and this issue of the way the glass vibrates. Note that the glass is divided into that Director retired and he had a long delay before the will be taken up at the GMI organization meeting in Paris. 4 to 8 vibrating segments that move in opposite directions. The Since the vibrational modes of glasses or bowls have both new Director had firmed up his plans for the organization. Once the possibilities are established with details, we will poll vibration amplitudes are maximum at the rim. normal and tangential components, they can be excited by Thomas has done an amazing job considering that he has the entire membership to get their preferences. either a normal or a tangential force. Glass harmonicas are been touring the world giving concerts at the same time On another note, the feature article in the last issue on usually played by rubbing the rim of the glass or bowl that he has been doing his planning. the “Tutor for the Musical Glasses” was not complete. We are tangentially with a wet finger, but striking the glass Thomas has taking numerous steps to minimize the including the completed text as an insertion in the issue. with a mallet or bowing it radially with a violin bow cost of the festival to GMI and its members. These include Finally, I wish to point out that the 2005 dues are now also sets it into vibration. negotiating for good rates and using his own time, efforts, due and if you would send them in to Alisa in a timely man- Rubbing a glass with a wet finger excites vibrations and resources. These steps along with the fact that we ner it would be greatly appreciated. The dues allow us to in the glass through a “stick-slip” process, much as a have not had a festival in five years led to our being able to print and mail these newsletters as well as helping us reduce eliminate the normal festival registration fee for members the costs associated with festivals. for “La Marche de l’Empereur”, a TV documentary. That GMI Happenings is the theater where he played “The Black Rider” by Tom – By Elizabeth Mears – Waits, William Burroughs and Bob Wilson, with Marianne As our February festival in Paris approaches, I assume that Faithfull as the main singer, a French young female popular Fig. 1. Holographic interferograms of 3 modes in a our membership is entertaining the public with glass music singer who won the “Victoire de la Musique” last year (the wineglass. [1]. around the world. equivalent of a Grammy Award). Then, Rene-Marc Bini pro- posed that he record “Nom de code DP”, a TV fiction based The modes shown in Fig. 1 are not harmonic. The frequen- From Lynn Drye, Prescott, Arizona, we learn that she on the preparation of an attack by terrorists. In December, cies of the first six modes [1] are in the ratios of approximately gave two performances of the Johann Friedrich Reichardt he recorded for the soundtrack of a new musical, “Fantomas”. 1 : 1.89 : 3.21 : 4.88 : 6.96 : 9.23. Striking the glass with a Fig. 2 “Rondeau in B-flat Major for Glass Harmonica, String Quartet, He played the Mozart K.617 and various works in Holland, mallet will excite all of these modes and more, but rubbing the and Double Bass” with the Prescott Strings in November. The played for the 20th anniversary of the TV channel Canal + in rim with a wet finger excites only the lowest mode and its har- moving violin bow excites a violin string. During part of a performance was very well received by both the audience and November, and will spend all January in Sydney Festival, still monics [1]. (This fact is not clear in some articles about glass vibration cycle, the rim of the glass at the point of contact the members of the Prescott Strings. She now has the entire with Waits, Burroughs, Wilson and Faithfull. Thomas has harmonicas). moves with the finger; during the balance of the cycle it score notated (from manuscript) and will be sending it to recently released four new CDs, including two with the glass Each point on a vibrating wineglass moves differently as it loses contact and “slips” back toward its equilibrium posi- Thomas Bloch for inclusion in the GMI Library collection. harmonica : vibrates. The holographic interferograms in Fig. 1 show only tion. This results in a sound that consists of a fundamental • MOZART / COMPLETE QUINTETS VOL. 4, Ensemble the axial motion (motion normal to the surface of the glass).