Sonorous Implementation of Wind Instruments of the Basque Folklore
Erica Macho Stadler, Mª Jesús Elejalde García Departamento de Física Aplicada 1, Escuela Técnica Superior de Ingeniería de Bilbao (UPV/EHU), Alameda de Urquijo s/n, 48013 Bilbao, Spain [email protected], [email protected]
One of the effective ways of improving the knowledge of physical aspects of autochthonous musical instruments is trying to bring together acoustical characterizations, the experimental one and the theoretical one, next to the data reported by manufacturers and interpreters. The aim of this work is to integrate a set of complementary data concerning the optimisation of some wind instruments of Basque culture, in order to improve the sonorous quality and the instrumental control. For this purpose, the experimental work is based on the observation of the shift in the resonance frequencies produced by small perturbations in the idealized active element.
1 Introduction Modelling and acoustical Many of us could accept that the traditional improvement instruments deserve time, work and dedication. To Basque instruments sustain this idea, the reasons can be historical, social, Flutes Silbote economical, musical, etc. Basque culture has Txistu Txirula developed its own musical instruments. Systematically, Single reed Alboka (double clarinet) these instruments have been played in the rural areas in Double reed Dultzaina, Suprinu, “fiestas”, concerts and dances. In addition, a lot of Txanbela Basque composers have dedicated their compositions Free reed Trikitixa Accordion to them. In most cases, these compositions are minor Instrument Players musical works, although sometimes a little masterpiece Manufacturers and and appears. Nowadays, some instruments have obtained Tuners Musical educators their own place in chamber music [1]. This work is included in a project that intends the modelling and acoustical improvement of Basque Figure 1: Project main ideas traditional musical instruments by means of the interaction between the acoustics investigation work and the knowledge of instrument manufacturers and tuners, players and musical educators. The project 2 Instruments description objectives are to advance in the modelling and acoustical improvement of flute type instruments 2.1 Flutes (txistu, txirula and silbote), reed instruments (alboka, dulzaina, supriñu, txanbela) and free reed instruments The Basque flute family is composed by three (accordion, trikitixa), and to create multimedia instruments: Silbote, Txistu and Txirula [1, 2, and 3]. materials in order to contribute to the musical acoustic The txistu is a three holed flute, tuned in F. The knowledge spreading. Figure 1 shows a schema of original instrument was the flute used by the Basque these ideas. minstrels. Through the years, some changes have been We want to obtain “modified instruments” with better made: a metallic mouthpiece was added and different acoustical properties and easier player’s control. As an materials have been used (bone, wood, plastic, metal, example, we can cite the tuning of the txistu correlative etc.). intervals as a result of the collaboration between The instruments manufactured today and those acousticians, constructors and txistularis (players) [2]. manufactured 30 years ago are very different. A more This work is focused on the tuning of some wind natural tuning has been achieved that permits the txistu instruments of Basque culture, in order to improve the work with other instruments of orchestra. sonorous quality and the instrumental control. The txistu produces almost three complete scales by For this purpose, at present the experimental work is combination of its holes and the production of based on the observation of the shift in the resonance overtones. The harmonic series of txistu sound are frequencies produced by small perturbations in the quite rich in overtones number for all the instrument idealized active element. fingering. This characteristic permits to obtain all the
447 Forum Acusticum 2005 Budapest Macho Stadler, Elejalde García
notes of the scale changing the air pressure blown perturb them, we use little weights of different masses through the pipe. that we move along the reed, and we study the effect of With the three holes covered, so all the pipe vibrates, adding a mass versus the position. we obtain the first harmonic, the fundamental D. The following overtones (D, A, D, …) can be produced increasing more and more the blowing air pressure. When the first hole is open the fundamental E and its overtones (E, B, E, …) appear depending on the air pressure. Opening the second hole the fundamental F and its overtones (F, C, F, …) appear depending also on the air pressure. Figure 2: F tuned txistu
2.2 Free reed instruments
The trikitixa is a diatonic accordion but also the ensemble of several Basque instruments, like the txistu, the alboka, the pandero and the accordion [1, 4, and 5]. This accordion has 23 melodic buttons in the right hand and 12 bass buttons in the left one. Each bass button produces a unique note, whereas each melodic button produces two different notes. This quality Figure 3: Accordion reeds enhances the instrument versatility. The sound generators of the accordion are the free reeds stimulated by the airflow supplied by the 4 Results bellows. The basic constituent elements of the reed are a plate, the own reed (or tongue) and the rivet. The not riveted end of the reed is free to vibrate from one side 4.1 Study of the effect of the and the other of the slot. The reed will only vibrate narrowing of the txistu bore in the when the air comes from the side of the plate on which resonance frequencies the reed is fixed. But on the other side of the plate there is another tongue that will vibrate when the air We have analysed the effect of a narrowing in the final comes from the opposite direction. The pitch of any bore region. The studied area extends 10cm from the note is determined by the natural frequency of the bore end. This zone includes two of the holes of the corresponding reed. instrument, placed at 5.5cm and 8.5cm from the tube end. Modifying the perturbation position and its size, the 3 Experimental frequencies can be varied in a controlled way. Experimental results show that the frequency of a The experimental work is based on the observation of sound is mainly modified when the perturbation is the shift in the resonance frequencies produced by located near the end of the resonant air column. When small perturbations in the idealized active element: the the sound is obtained with all the holes closed (D), the section of the instrument cylindrical bore or the reed. A maximum frequency variation is obtained with a preamplified microphone (Bruel&Kjaer 4189) perturbation situated at the bore end, whereas for the connected to an analyser (Bruel&Kjaer PULSE) note E the maximum frequency variation is obtained permits to examine the waveforms in detail. with a perturbation situated near the first hole, behind For the Basque flute family the studied instrument is a it. In a similar way, for the sound F the maximum standard txistu, showed in Figure 2. The air column in frequency variation is obtained with a perturbation the tube is excited by blowing. In order to change the situated just behind the second hole. tube section, we use some rings of diverse thickness The obtained results agree with the theoretical and length that we move along it, and we study the calculations that predict that a narrowing in a zone of effect of a narrowing versus the position. maximum velocity produces a lowering in the In the case of the free reed family instruments we have frequency [6]. studied some accordion reeds. We investigate the Table 1 shows experimental results for a perturbation frequency change of the first resonance mode, by of 1cm of length and 0.1cm of thickness. The ring is perturbing the mass and the effective stiffness of the moved between the end of the tube and the second hole reed. The reeds are excited by blowing. In order to
448 Forum Acusticum 2005 Budapest Macho Stadler, Elejalde García
position surroundings in steps of 1 cm. Txistu inner The frequency shifts of the first and the second diameter is 1.4cm. overtones for each fingering are not the same, but both Analysed sounds correspond to the two first overtones can be perceived by a musician. As we know, the (fundamental and second harmonic) of three different perceptible threshold of frequency shift depends on the fingering: D obtained with the three holes covered, E instrument. On flutes, musicians are able to detect obtained when the first hole is open and F obtained deviations of less than 5 cents [7]. Fundamental opening the second hole. The value of the frequency frequency variation is always higher than the second harmonic one. This fact implies a variation in the for the instrument without any perturbation is f10 for the fundamental and f for the second harmonic, timbre of the obtained sound, added to the modification 20 of the instrument tuning. whereas f1p and f2p are the obtained frequencies when a perturbation is placed near the end of the resonant air column in each case. 4.2 Study of the effect of placing a Table 2 shows frequency ratio of the second and the small mass at a point of the reed in the first harmonic for the unmodified txistu and the resonance frequencies perturbed one. It can be seen immediately that the presence of a perturbation varies the instrument tuning. We have analysed the effect of the mass m along the entire reed. Modifying the perturbation position and its Table 1: First and second harmonic frequency with (f1p, size, the frequencies can be varied in a controlled way. f2p) and without (f10, f20) perturbation. The perturbation Experimental results show that the frequency of a is placed near the end of the resonant air column in sound is mainly modified when the perturbation is each case. located near the free end of the reed. The obtained results agree with the theoretical D E F calculations that predict that a loading mass produces a lowering in the frequency [8]. ●●● ●●○ ●○○ Figure 4 shows experimental results for a perturbation
f10 (Hz) 418 470 513 of m=0.23g in a reed with M= 0.68g (m/M=0.33). The mass is moved between the free end and the clamped f (Hz) 411 463 507 1p end of the reed in steps of 0.5cm. Reed length is 4.2cm. Frequency 29 26 20 shift (cents) 0 1 f20 (Hz) 832 930 1030 0 f2p (Hz) 823 919 1023 Frequency 19 21 12 shift (cents) Perturbation End of the Next to Next to position tube the first the second hole hole Distance to 0 cm 6 cm 9 cm the tube end (cents) Frequencyshift -700 x/L Table 2: Second and first harmonic frequency relation without and with perturbation. The perturbation is Figure 4: Typical result for the relative frequency placed near the end of the resonant air column in each change in the first resonance mode of a reed of length case. L versus mass position x.
D E F When we compare the slope of graph similar to Figure 4 for different values of m and/or different reeds, we ●●● ●●○ ●○○ observe that the slope varies with the relative mass m/M, as it can be seen in Table 3. f20/f10 1.99 1.98 2.01
f2p/f1p 2.00 1.98 2.02
449 Forum Acusticum 2005 Budapest Macho Stadler, Elejalde García
Table 3: Slope of the relative frequency change in the search for communications in order that make the first resonance mode versus mass position graph. research results available to instrument makers and other interested people. In this field we create multimedia materials in order to contribute to the m/M 0.05 0.19 0.33 0.44 0.80 musical acoustic knowledge spreading [10]. Slope 2026 1378 1085 804 166 References The higher slope value appears for m/M=0.8, and diminishes when m/M decreases, taking the lowest [1] http://www.basquearts.com/culture, value for m/M=0.05. The dependence seems to be quite BasqueArts&Culture website. linear. [2] A. Amilibia and J. Alonso, ‘Análisis Acústico del These results agree with the common practice to load Txistu y Ajuste de Intervalos’, pp. 9 31, Servicio some accordion reeds in order to maintain the Central de Publicaciones del Gobierno Vasco, instrument weight under reasonable limits: some reeds Vitoria, ISBN 84 457 1574 7 (2000) are loaded in the tip and sound as low as other with higher length [9]. [3] http://www.txistulari.com, A website about the Txistu. When exposed to the flow of air supplied by the bellows, the reed, having little resistance, will vibrate [4] http://www.trikitixa.net, A website about the with a frequency just below the frequency of lower Trikitrixa. resonance of the fixed free bar. Apart from this, due to [5] R. Llanos Vázquez; J. Alonso Moral; M.J. the non linearity of the problem, a great number of Elejalde García; E. Macho Stadler, ‘Interaction harmonics of that frequency is found, instead of the among physical acoustic knowledge and non harmonic overtones expected for a free fixed bar performance in the accordion and its educational vibrating freely after being disturbed from its side’, Proc. Stockholm Music Acoustics equilibrium position [6]. The harmonics of the first Conference 2003, Stockholm, Vol. 2. pp. 549 552 resonance mode of the studied reeds behaves in a (2003) identical way than the first one, being Figure 4 the same for all of them. This fact implies that the reed [6] N. H. Fletcher and T. D. Rossing, ‘The Physics of timbre does not vary with the charging mass. Musical Instruments’, Springer Verlag, ISBN 0 387 98373 0 (1988) [7] C. J. Nederveen, ‘Acoustical aspects of woodwind 5 Conclusion and further work instruments’, Northen Illinois University Press, ISBN 0 87580 577 9 (1998) In this work we have study the tuning of some wind instruments of Basque culture, in order to improve the [8] R. Llanos Vázquez; J. Alonso Moral; M.J. sonorous quality and the instrumental control. Elejalde García; E. Macho Stadler, ‘First suggestions for the improvement of accordion Our results show that when we introduce some reeds’, Acustica, Vol. 88. Supl. 1. pp. S84. (2002) controlled perturbation in the instrument active element, the frequencies can be varied in a controlled [9] T. Benetoux, “The Ins and Outs of the Accordion”, way. The obtained frequency shifts can be perceived Self Published, Le Thor , ISBN 2 9517184 1 1, by musicians without any difficulty. In the txistu, we (2002) have perceived changes of the sound timbre with the [10] M.J. Elejalde García; E. Macho Stadler; A. perturbation presence. These results will be Franco García and J. Janariz Larumbe ‘Didactic complemented with additional studies on timbre resources for the teaching and the popularization variation and the effect of the combination (coupling) of the Physics of the Music’, Proc. Stockholm of two or more perturbations in the same element. Music Acoustics Conference 2003, Stockholm, This work is included in a project that intends the Vol. 2. pp. 719 722 (2003) modelling and acoustical improvement of Basque traditional musical instruments. The objectives are to advance in the modelling and acoustical improvement Acknowledgments of instruments by physical modelling, instrument constituents’ optimisation, construction material, etc. This work was supported by the Basque Country We consider very important the establishment of a University (1/UPV 00057.345 E 15903/2004). closer co operation in this field with instrument makers, players and musical educators. Moreover we
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