Roberto Velázquez Cabrera

First version May 2000. Last update March 2002

The Spanish version of this paper was presented in the Computing International Congress CIC-2000, IPN, Mexico, November 16/2000.


Introduction and background

The objective of this work is to prove the viability of a previous study recommendation [Velázquez-Cabrera, 2000], taking advantage of a proposed methodology, to help in the analysis of relevant Mexican aerophones. The case is an extraordinary aerophone of black stone collected by the deceased anthropologist Francisco Beverido Pereau, who realized important archaeological discoveries and was the photographer of the "Museo de Antropología" of Xalapa, Veracruz. He was also the photographer of the book "Caritas sonrientes" [Paz, 1971], with texts from poet Octavio Paz and a description from archaeologist Alfonso Medellín. Beverido took the pictures included in Charles Boiles´s article "Flauta triple de Tenenexpan" [Boiles-Lafayette, 1965], and he has other important publications.

The Beverido family let me look for pictures and studies of aerophones from Gulf Zone in the anthropologist's office and library. They gave me a book "Estética Olmeca" [Beverido-Pereau, 1996], several beautiful pictures of Totonacan clay sculptures and they lended me the book "Cerámica de Totonacapan" [Medellin-Zenil, 1970]. In this search, it was found the little black stone, together with several beads. It had not any archaeological information of origin and description, but maybe the construction and material called the attention of the anthropologist. It seems that he did not considered it to be relevant, since he did not take pictures, neither it was analyzed and catalogued as other archaeological goods collected by him and provided to the museum.

When I saw it, I identified it as a possible aerophone. When it was played, it generated loud sounds similar to noise and wind (but distinctive from aeolian tones). The simple visual analysis indicates that it is an ancient aerophone, for several reasons: one is the shape of its holes or tubes that could not be made with a common conical bit. The most important criteria for its particular and exact structure is unknown. In other words, there is not an ancient artifact of this type from which we could make a copy.

It was a pleasant surprise to find this drilled little stone, since I had a special interest in this kind of Mexican wind aerophones (which appear to the untrained ear cacophonous, althougt they work with air and generate wind). I had been looking for an ancient aerophone to make a study. I did not look to find one in the office of a professional anthropologist and photographer.

More than 50 years ago, I made my first aerophone with a "corcholata" (metallic plug for soda and beer bottle), flattened, bent and with two holes near the center, like the one shown in Figure 5. The metallic plug (with out the cork), was lightly flattened with a hammer and then fixed (with a chewed gum) on railroad, to be very well flattened by the wheels of iron. Kids from my home town (Tequila, Jalisco) used to play with this "zumbador" (buzzer) or "gallito" (little cock), operated with a cord introduced in the holes and tied. The cord was sustained with the annular fingers of the two hands, with a circular movement the cord was twisted and when it was stretched and relaxed the flattened plug rotated to a great velocity in one direction and then in the contrary. The game was between two players, face to face, to cut the cord of the adversary. These toys dobled (with out the cord and with the two holes located in a near distance face to face) to become another toy. The new play was a competition to see who could make the loudest sound. This sound is very rich in composed of high frequencies, maybe due to its special small simple, flattened and open resonating chamber and its two holes of small length (or thickness of the wall).

Some years ago, when I started the study of Mexican aerophones, I realized that these toys were similar to those used in Ancient Mexico (actual zone from south of USA to Nicaragua). In my opinion, the Florentine Codex illusttates one of this type, that can be seen in the upper left corner of Figure 1.

During the last two years, I have researched more than one hundred experimental wind aerophones (a family that may be called Mexican noise generators) of several shapes and structures, some of them with similar design, but none exactly like this drilled little black stone, which seemed unique. There are some artisans (as Gregorio and Mario Cortéz brothers, from Santa Cruz de Arriba, Municipio de Texcoco, Estado de Mexico) who know how to make aerophones of this type although of a different design.

To a researcher who has most studied this family of aerophones - José Luis Franco [Franco, 1962]- this artifacts were "aerófonos con fuelle de aire" (aerophones with spring of air). He also studied aerophones of the Gulf Zone [Franco, 1971].

This family type of aerophones had been directly analyzed by other researchers who had access to them, like Susan Rawcliffe [Rawcliffe, 1986], who has been analyzing ancient flutes, and built and playing her sound sculptures for 25 years. In her article was included a set of drawings with views of sections of aerophones of several museums and collections, made by the artist Jim Grant on the base of a careful visual analysis of the aerophones made by herself. Included is a brief analysis of an extraordinary aerophone with thee chambers, the "Gamitadera", called by her a "chamberduct flute". Rawcliffe comments: "The sound of this type of instrument is extraordinary, varying from a raspy throat gurgle to wrenching cry, depending on construction and on performance practices". There are many other flutes that have a chamberduct. The author has analyzed replicas of the "Gamitadera" in a previous study [Velázquez-Cabrera, 1999]

Jorge Dájer included in his book [Dájer, 1995] a picture of one, described as an "ocarina" (figure 2), similar to one included in Florentine Codex (Figure 1). Dájer provides the following comments:

"The free intonation in this ocarina made of bone is controlled by the tongue changing the mouth cavity, forming with this a chamber, needing practice to acquire the knack of playing. It comes from Araró (Michoacan) and is part of the State Museum´s special collection where it has been classified as shuttle (Num. 4749)".

The designation "Ocarina" was, however an inaccurate description of these artifacs, since they do not have closed resonating chambers, or tone holes.

The round stamp or button with a glyph, about 22 millimeters, was included in his pictures to give an idea of the artifacts size. They told me that it was stolen in an exposition (The author appreciates this design so much he uses similar one for making drawings and clay artifacts).

The few analysis made of this family of "Mexican noise generators" includes only very general descriptions, pictures and drawings. The "Museo Nacional de Antropología", in México City, shows one x-ray negative picture of a Maya artifact of this type.

General Analysis

Beverido family permitted me to make the first direct study of a Mexican ancient aerophone, using tools and procedures previously proved with experimental replicas. The most recent case was the Virtual Analysis of Gamitadera [Velázquez- Cabrera, 1999].

The aerophone of black stone illustrated in Figure 3 is relevant for several reasons: most important, it constitutes the first aerophone discovered of this type crafted with hard stone (it also contains metal causing a high specific weight); secondly, it clearly revels it's internal structure, making x-ray examination unneeded, as it is current practice for other complex aerophones of this type; thirdly, it is the smallest known of this general style and; fourth, it is drilled with round holes or channels (with an interior shape like a tube with round holes or channels), which relates to other Mexican aerophones of wood, bone, metal and stone, similar to the one included in Figure 1 and other different (whistles, ocarinas and flutes), but with their windows, edges and chambers made with 4 conical drillings of different sizes.

Design structure

Figure 4 shows a draft with the principal views and sections of the aerophone. The frontal view shows the part where the sound is generated. The section A-A´ shows the detail of the resonating central cavity and the exit, and one lateral hole (or channel), equal and face to face to one of the opposite side (4 mm in diameter), where the sound is generated). The section B-B´ shows the detail of these holes (in the upper and lower part) and the resonating cavity viewed from the top. This section is used to show the playing technique (Figure 6). The three short channels or tubes are centered horizontally but a tittle lower vertically. The front view indicates the anterior diameter (9 mm) of the exit hole. It is bigger than one in the back (5 mm).

This simple sketch is relevant, since with this information it is possible to elaborate very similar replicas of the original. A similar sketch or drawing neither was discovered in the literature, among the thousands of ancient aerophones that had been found. In the best drawings, only one section view is provided without the dimensions, capable of providing insufficient information for the purposes of explanation.

I made replicas of the original aerophone of black stone aerophone on several materials like clay and wood (Figure 5) that can produce similar sounds. This work proved that it is possible to build good replicas, if we have the original artifact, the ability to work the required materials, and the systems to measure and analyze their sounds. This exercise is relevant because no similar studies seem to have been recorded.

Main element and functioning

Figure 6 shows the elements and scheme of functioning of the aerophone, to produce the loudest sound. It must be played as shown in cutting B-B´ of Figure 4, located inside the mouth, between lips and teeth, and the tongue closing the back hole. The organological elements of this aerophone-mouth system are:

  • Mouth channel 1, formed between palate and tongue, to input the air flow (showed by the arrow);
  • Aerophone with the main resonating cavity B (as an open tube) and two holes (tubes A and C), located face to face, in a vertical axis. The inner circle of this holes may be two especial circular edges, where the sound is generated.
  • Mouth cavity 2 (that may work like a Hemholtz´s irregular resonator)

In the beginning, the sounding mechanism might works as follows:

  1. The strong flow of air (coming from mouth channel 1 and showed by the arrow), goes into the upper hole (channel) A.
  2. In the exit of hole A the compressed circular air flow may be expanded, because the main chamber B is open and has less pressure. And may occur diffractions, because the aperture is small.
  3. The expanded waves go to the opposite side of chamber B and to the circular edge of hole C, generating reflections to the back.
  4. The main strong flow of air, that is coming from hole A, pass throw hole C and go to mouth cavity 2, that acts as a mass-spring system, generating resonating reflections to the back.
  5. When these reflections cross to the hole C more refraction are generated inside the main resonating chamber B.
  6. In few milliseconds, the combination of reflections and refractions (and expansions), in both directions, with the two circular edges in a reduced space, may generate a complex and turbulent dynamic of waves, pressures and sounds, that produce the noise than is showed with virgules (Mexican graphical symbols for all kind of waving being and phenomenon, like sounds).
  7. Two groups of frequency components of the noise are amplified by the two resonating chambers, as it can be seen in the two wide peaks of the spectrograms (figures 7, 8, 9 and 10)

It can produce other sounds, if it is played in other ways. For example, rotated 90 degrees and set outside in front of the lips with the air flowed by his back hole, and closing with afinger its front hole, their lateral holes are converted as exit holes for the sound.

Analysis of the sounds.

In the following, the spectrograms are shown in 2 and 3 dimensions (2D and 3D) of Figures 7 and 8, respectively, of a sound or noise, played in a simple way. The sound was registered with a microphone and a personal computer with a sound card type "Sound Blaster", in a file format Wav compatible with Windows 95 operating system. The spectrograms were generated with programs downloaded from Internet [Horne] and [Volkner], that uses a routine of FFT (Fast Fourier Transform), applied to the digital file. The graphs show that there are frequency components (Hz) and relatively high intensities (dB) very complex. The maximum level of their peaks or crests are given near 2 kHz and 6 kHz but the generated frequencies cover a wide range from less than 20 Hz to more than 10 KHz similar to a colored noise.

In Figure 8, we can observe that the resulting signals in the lower frequencies have considerable magnitudes. To observe characteristic details of the signal, Figure 9 shows the power spectrum of the same sound. In these graphs the scales are not linear, the Hz are duplicated each octave as it happen in music. This is because the used program [Volkner] is a tuner for musical instruments. The intensities are given in dB, in a logarithmic scale relative to the perception properties of human being neither represents a linear scale.

Using other programs [Sat 32], it was possible to elaborate other graph (Figure 10) in which the frequencies and amplitudes are given in linear scales and units (like EU**2 instead of dB), the greater frequencies in intensities are noted with better clarity, since lower levels are reduced considerably.

Conclusions and recommendations

  • This exercise proves that the proposed organological and acoustical analysis may be effective to analyze original (authentic) Mexican aerophones and can be of utility to support opinions on the authenticity of archaeological sound artifacts.
  • As the spectrograms obtained are similar to other members of the family "aerophones of spring of air" or "of wind" analyzed previously, in intensity and in frequency components, it confirms that the unknown little black aerophone is an original (authentic) ancient artifact, and belongs to this group of noisy aerophones. Also, It was proved that the spectrograms can be used to evaluate the sound fidelity of copies or replicas with complex non periodic sounds.
  • Spectrogram is the best technique to make visual analysis (in frequency domain) of non periodic complex signals like these Mexican sounds that I could find available openly in Internet.
  • It is important to make an analysis of all known parallel aerophones in stewardship of museums and collectors, to expedite be their comparison and correlation. The method is applicable by others, is easy, simple and cheap (because requires only a personal computer and the programs are openly available in Internet).
  • It is necessary to inform the museum of Xalapa, to see if they are interested in the analyzed aerophone of black stone and its possible exhibition and explanation.
  • The detailed dynamics of the sounding mechanism of this family of complex "Mexican noise generators" is unknown. Its determination is a work for advanced research. From the mathematical point of view, it seems that this system may be represented by a stochastic-non linear-dynamic model operating with a wide range of non periodic vibrations of pressure and sound waves, with two resonating chambers (one of them very small) and two special circular edges, as a chaotic and turbulent process. This kind of models is in the frontier of the research of several advanced techniques, as fluid vortex dynamics and scientific visualization.
  • Also, the anthropological and cultural elements of these noisy aerophones are unknown, from their original name to their ancient use.


Notes of some advanced techniques, found in Internet.

There are advanced techniques to analyze complex systems of fluids, as those of the generation of sound in tubes (organs and flutes), using digital computers and elaborated mathematical models and numeric solutions. But they are not easy to adapt in Mexico for complex aerophones analysis.

Advanced Techniques using computers

A good example of this is the following: Panayotis Skordos in his extraordinary doctoral dissertation at MIT [Skordos, 1995] made simulations of a 20 cm long soprano recorder (without tone holes), using 20 computer workstations in parallel during three days, to obtain 25 milliseconds of isocontours of vorticity after startup of the a tone produced near 400 and 1100Hz (Figure 11).

After I read his study, I sent an e-mail with my congratulations for his research and to inform him about my thesis in Spanish. I asked him for permission to use some of his graphs and to know how difficult it would it be to use his program to analyze complex aerophones with several irregular chambers, in other computer networks. He wrote his answer:

"Thanks. As I do not know Spanish, I will have to wait for your English paper later. Yes, you can include graphs, pictures, etc. from my stuff (it's an honor for me) as long as you have a reference and say where you took it from. The model is direct simulation of compressible subsonic fluid flow (the full Navier Stokes equations), and it can certainly be applied to complex sound artifacts. However it will take some work to do it correctly and lots of computer time. I expect it will be a lot easier in 10-20 years with much more powerful computers. To use my programs in other networks, I assume you mean to run my fluid-flow simulations in other computer networks. If I was doing it, it would not be too difficult (especially if it was a UNIX network). But for someone else it would be very difficult, and require very good computer skills. You are talking about setting up an advanced CFD simulation system. It is not trivial. Also I am not working on this anymore so I can not help. Best wishes on your research."

There are other limitations: the cost of the workstations ($50 k US dollars), the programs are not available, the simulation was made only in two dimensions and not in real time. It seems that this extraordinary study was not continued or followed by others.

Other advanced methods.

There are other methods that have been used, from the beginning of this century, to analyze the vortex dynamics in real time of wind musical instruments as tubes of organs, flutes and whistles that could be used to study complex aerophones. They used smoke and stroboscopic pictures, but these facilities were unavailable in Mexico for such experiments.

There are also important studies related with the recognition of musical notes and human phonemes and words from speech, but the equivalent elements of complex ancient aerophones and their possible meaning, are unknown.

I did not find any literature on these methods, or any other, applied to complex ancient aerophones.

I found only one study [Garret and Statnekov, 1977] of ancient aerophones that includes the Hemholtz´s equation for globular resonators. They used a spectrum analyzer but it seems that their main conclusions were obtained with physical measurements of the sounds.

Magazines interested in ancient sound artifacts

On Internet, I found only one magazine with few articles on ancient aerophones. "Experimental Musical Instruments", but last year they decided to end the publication of the magazine. ( The former Editor, Bart Hopkin, told me that he does not know any other magazine interested in ancient sound artifacts.

In a Hopkin´s book [Hopkin, 1999] is included one equation applied to globular resonators as ocarinas, whistles and horns with al least one circular tone hole, in addition to the mouth. He informed me that this equation was provided directly by Dr. John W. Coltman*, who told me that its derivation is in a book [Fletcher & Rosssing, 1991] and how to interpret and use the formula.

f =(c/2*PI)*square root [((a1/te1) + (a2/te2) + ....)/v]


f = resonance frequency

c = velocity of sound on air

PI = 3.1416

v = volume of resonator cavity

a1 = area of mouth and a2, a3, etc. are areas of additional tone holes.

tei = effective length of holes or thickness of the wall = L + k * d , k may vary between .75 to .85

d = diameter of circular hole

L = Length of hole or thickness of the wall

It seems that this equation can not be applied to resonators with complex non periodic sounds, but is adequate to estimate the frequency of globular resonators with several circular tone holes, that can be made in any location on the chamber wall.

The Hemholtz´s equation is very important for ancient aerophones because many whistles and ocarinas have a globular resonator.

Situation in the archaeology.

The state of the art for the analysis of ancient aerophones in archaeology, can be shown with an extraordinary discovery and study of six 9000 years old flutes, made of bird's bone, found in an excavation at Jiahu of the Neolitic site in Henan Province of China [Zhang, Juzhong Harbattle and German, 1999], published in Nature magazine, on September 23 of 1999. The project was supported by the National Natural Science of China, the Department of Science & Technology of China, The Chinese Academy of Science and the Structure Research Laboratory at USTC. Research at Brothaven National Laboratory, supported by the US Department of Energy.

During research at the Brothahaven National laboratory, (which is supported by the US Department of Energy), it was found that important archaeological information and material (dated with C14 technique), and cultures originated the aerophones. For the anlysis of the sounds they used a "stroboconn" to measure the pitch of the sound of the best preserved instrument (which was free of cracks) that remained playable. They found that their notes and scale are similar to those of familiar music. Ergo, their ancient users could be Neolithic musical performers. In addition, they conclude:

"It should be possible, by constructing exact replicas of the Jihau flutes in material whose density approximate bird-bone, to study the tonal sequence of all these instruments without endangering the valuable artifacts themselves".

To use of replicas was a method long adopted by the author to study Mexican ancient aerophones (however, independent researchers were not permitted to study the museum’s own ancient artifact directly).

To study the tonal sequences of flutes is important anthropological and archaeological imperative; and the stroboscope (now part of the history of the technological examination of sound) measures accurately the pitch of a musical note. II found a picture also on the Web of one strobosconn (technology developed in 1936) located at (href=" In México, too, there is a stroboconn is in a museum of metrology, having been previously used in the "Escuela Nacional de Música".

With the Wav file of an ancient song from China "little cabbage" played with the flute (available in Nature magazine) and the program Gram (used in the paper), it is possible to obtain the spectrogram of a 9,000 years old striking sound, recorded with more noise of lower frequencies (figure 12). The spectrogram of the two musical tones seems a Spartan ancient Greek or classic signature, as a graphical symbol used to represent all kind of waving beings and phenomena, like the sound.

There are similar bone flutes in other countries as Peru and México, but their technical analysis remain to be done. Similar situation exists in the rich organology of thousands of ancient wind artifacts from all over the word, with the exception of modern wind musical instruments.



  1. Bart Hopkin "Air Columns and Tone Holes" , published by Thai Hei Shakuhachi, 1999.
  2. Beverido, Francisco, Pereau. " Estética Olmeca", Biblioteca Universidad Veracruzana, Xalapa, Veracruz, México.
  3. Boiles-Lafayette, Charles. "La Flauta Triple de Tenenexpan". La Palabra y el Hombre, II, Epoca 34, Revista de la Universidad Veracruzana, Abril-junio de 1965.
  4. Dájer, Jorge. "Los artefactos Sonoros Precolombinos, Desde su Descubrimiento en Michoacan", FONCA-ELA. México. 1995.
  5. Flecher & Rossing, "The Physics of Musical Instruments", Springer-Verlag, 1991.
  6. Franco, José Luis, "Flautas de Muelle de aire", Excélsior, México, 14 de octubre de 1962.
  7. Franco, José Luis, "Musical Instruments from Central Veracruz in Classic Times", Ancient Art of Veracruz, Exhibition Catalog of the Los Angeles County Museum of Narural History, 1971.
  8. Garret, S. and Statnekov D. K., "Peruvian Whistling Bottles", The Journal of Acoustical Society of America, Vol. 62, No. 2, August, 1977. (
  9. Horne, Richard, Spectogram V 5.0.9, Gram ( Richard Horne autorized me to use his excellent freeware program in my studies to obtain spectrograms in two dimensions
  10. Liangson He, Signal Analyzer Toolkit V.2., Sat32. It was used during the time allowed for testing(
  11. Medellín-Zenil, Alfonzo, "Cerámicas de Totonacapan. Exploraciones Arqueológicas en el Centro de Veracruz". Universidad Veracruzana, Instituto de Arqueología, Xalapa, Ver. México, 1960.
  12. Paz, Octavio, Medellín, Francisco y Beverido Francisco. "Magia de la Risa" Sep/Setentas, 1971.
  13. Raucliffe, Susan. "Complex Acoustics in Pre-Columbian Flute Systems", Experimental Musical Instruments, Organology, Vol. III, #2, 1986. She published other book "Musical Repercussions of 1942: Encounters in Text and Performance", Smithsonian Institution Press, 1992.
  14. Skordos, P. A.,"Modeling flue pipes: subsonic flow, lattice Bolzmann, and parallel distributed computers", (3MB 360 pages) Ph.D. thesis , MIT Department of EECS, Articial Intelligence Laboratory, February 1995. (
  15. Velázquez-Cabrera, Roberto, "Estudio de Aerófonos Mexicanos Usando Técnicas Artesanales y Computacionales. Polifonía Mexicana Virtual", CIC, IPN, January 2000. Last draft of a MD Thesis in computation. Available in Internet location:
  16. Velázquez-Cabrera, Roberto. "Análisis Virtual de la Gamitadera", 1999. Study with replicas of an extraordinary aerophone with tree resonating chambers, from the Olmec culture of Gulf Zone.
  17. Volkmer, D., "TUNE!IT", ( Shareware. This program was used to obtain the spectrograms in three dimensions, during the time allowed for testing.
  18. Zhang, Juzhong Harbattle and German, Oldest playable musical instruments found at Jiahu early Neolitic site in China, NATURE, Vol. 401, Num. 6755 pp 366-368, 23 sep. 99. (


* The English translation of this paper was made especially for Dr. John W. Coltman, because he had curiosity in the black stone aerophone. I was glad to send him several replicas of this type for his collection of flutes and for his experiments, because he is the first international expert that showed interest in the matter. The last update of the English text has corrections provided by Baz Jennings, an expert in ocarinas (



Figure 1. Wind aerophone from Florentine Codex (Book VII. Miscoacalli instruments, Lam. 70)


Figure 2. Bone "ocarina" from Araró (picture by Dájer)


Figure 3. Picture of the black stone aerophone

Figure 4. Sketch with two views and two cuttings



Figure 5. Replicas of rigid materials (including a metallic cup of beer bottle)




Figure 6. Schema of functioning (operation)






Figure 7. Spectrogram in 2D of the same stone aerophone sound



Figure 8. Spectrogram in 3D of the same sound




Figure 9. Power spectrum of the same sound.


Figure 10. Other power spectrum of the same sound



Figure 11. Skordos´s computer simulation of a recorder




Figure 12. Spectrogram of a 9,000 years flute musical phrase