ORGANISTRUM. A short study about its possible repertoire.

ORGANISTRUM. A short study about its possible repertoire.

The Organistrum is always depicted in instrumental groups either related to the parade of King David (Old Testament) or to the group of the 24 elders of the Apocalypse (New Testament). The characters are in full robes, except for one of the two musicians from the Hunterian psalter (the one in charge of the crank, may be a servant). In the latter representation, in the capital of Boscherville and in the sculpture of Compostela, the musician who acts on the keys seems to have his mouth ajar, as if mid-song.

It is necessary to carefully analyze the few documents at our disposal in order to obtain as much information as possible.

Before I introduce this new phase of my research, however, let us recall the thoughts of two authors who had the same intuition about the function of Organistrum.

Francis W. Galpin in Old english instruments of music, 1910, states:  

"The Organistrum, for such was its name at first, is undoubtedly derived from the Monochord, a simple contrivance for ascertaining the intervals of the musical scale by a series of movable bridges".

Laura de Castellet in: The sound space: Thought, Music and Liturgy, in the volume: Spaces of Knowledge: Four Dimensions of Medieval Thought, Barcelona, ​​2014, writes:

“At any rate, the Organistrum was not conceived as a relative or a surrogate of the organ for the embellishment of sound within the temple. For instance, the presence of an organistrum amidst the twentyfour elders of the Apocalypse of the Gate of Glory … and at the collegiate church at Toro (Zamora), does not mean that such instrument leads any kind of concert, but that it symbolically represents the study of the language of sound, mathematical speculation, and cosmological order, and the approach to the divine essence. The elders are not making music, but rather preparing themselves - some of them are tuning their instruments- both intellectually and spiritually to face the advent of a new order of things. » p.39.  

According to both scholars, the Organistrum finds its origins from an instrument used to measure the pitch of sounds since ancient times.

However, in order to seriously consider the possibility that it played a significant role in musical practice too, it is necessary to identify its possible scope of use.




The context in which the instrument is described or depicted is always, and only, that of sacred music.

When it was still believed that the Organistrum had first appeared in the 9th century, it seemed to some to find an indirect reference within the treatise Musica enchiriadis.

The anonymous author meticulously describes a polyphonic practice called Organum parallelum. He states that the use of instruments was allowed in polyphony, so long as these strictly respected the voice pitches (Pia,2011). This encouraged some researchers to attribute to the Organistrum the role of Organum parallelum performer. They stated that two strings were tuned an octave apart and the third had to be tuned to the fourth or fifth (e.g. C3 – F3 /G3 – C4) (Rault, 1985). In other instruments one string is tuned to a fundamental pitch, the other two a fifth above (Kurt Reichmann). When operating a key all three strings are shortened.

Today, we know that the documents, correctly dated, place the lifetime of the Organistrum between the end of 11th and the end of 12th century. In this period, musicians were experiencing new forms of polyphony as the organum sillabicum (es. Ad organum faciendum, M.17sup., Bibl.Ambrosiana, Milan), organum melismaticum or floridum (codex of Saint Martial de Limoges and Magnus liber organi de Notre Dame), the discantus, the clausula and conductus (Codex Calixtinus and Magnus liber organi de Notre Dame).

It is impossible not to wonder whether the Organistrum had any relationship with such repertoires. If it did, we must then direct our attention to finding out how, with what tuning and using what type of scale.

The first element of judgment is the definition of the area of ​​sacred music as characteristic of all representations of the instrument.

The second is the diatonic scale indicated in the precious drawing by Gerbert.

The sacred music of the time theorizes and exclusively employs the diatonic scale - this must have been the scale of any musical instrument. The series of bells and keyboards of the Romanesque organs do not, in fact, include fictae other than the Bb.

The keyboard of the Compostela instrument, with eleven keys within the half of the diapason, and therefore apparently chromatic, could probably be organized as in fig.9.


                    A2      ---          B         C3               D                E          F                   G 


A3     ---       Bb        B        C4                  D                 E       F                 G4


                      A2       ---        B         C3               D                E          F                   G                    


0                    1        2         3*         4        5        6       7      8*       9      10        11  



fig.9  Diatonic  keyboard with 11 keys within the half of the diapason.


The nuts of the bass strings, both tuned in A2, are positioned further forward the nut of the middle string, tuned in A3, by the space of a semitone. The keys have hurdy-gurdy-like separate tangents and have vertical movement. Keys 4, 6, 9, 11 touch only the outer strings to play the notes of the lower octave. Key 1 acts on the central treble string passing under the nuts of the lateral strings. Keys 2, 3, 5, 7, 8 and 10 touch the treble string to play the notes of the highest octave. Keys 3 and 8 are the only ones enabled to act alternatively on the central string or on the side ones, after 90° rotation of the bar (fig.10).

The scale starts from A2, and not from C3 as in Gerbert, because A2 is the lowest note of the repertoire (cod. Pluteus, c.LXX r.), as can be seen from the analysis of the parts of tenor of the melismatic Organa in Magnus Liber Organi de Notre Dame. The tenor part’s highest note is generally D4, and only in very rare cases F4 (code Pluteus, c.LXVII r. And LXXXIIII, r./v.), while A4 appears only in non-melismatic compositions (code Pluteus, LXXXVIII r.).

In the first octave the Bb is missing, though this note is not foreseen in the Guidonian Gamut and consequently is not used in this repertoire. The natural B of the same octave is found, at least to my knowledge, only in one case (cod. Pluteus, c. CXXII).

To play the notes of the first octave, the player who turns the crank keeps the middle string away from the edge of the wheel. To continue on to the second octave, he moves the side strings away. All this to avoid using the Organistrum as a drone instrument, limited to only two modes at a time, in a style appropriate for secular and folk music performances.

Using the same string selection system, the compass from A2 to F4 - and up to A4 - can also be obtained with the 8 key diatonic keyboard, having the foresight to tune two strings in A2 and the third one an octave higher.  (In this case, however, the position of the sib would necessarily be at the beginning of the row and not, as in Gerbert's keyboard, at the end).

Should this system look too complicate we can imagine a shorter diatonic keyboard for Compostela Organistrum (long enough for playing most of the tenor parts of the repertoire) starting at A2 (all three strings), with no Bb in the first octave, reaching the eleventh key on D4 including Bb in the second octave. In this case the keys row would end visibly beyond the middle of the string (1/2 + 1/8 of diapason), the spacing of the keys couldn’t be regular as in the sculpture.

Nevertheless, no matter how structured, the diatonic keyboard of an Organistrum or a Romanesque organ could have been useful to the musician in order to check the right intervals while composing the vox organalis of organum melismaticum.

 (translated from Italian)

from the book:

Giuseppe Severini

"Organistrum. Un caso di archeologia sperimentale"
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Organistrum keyboard  from Portico de la Gloria, Santiago de Compostela.

Organistrum keyboard from Portico de la Gloria, Santiago de Compostela.

Symphonia / Organistrum


in Santiago de Compostela cathedral.

(Inquiry into a troubling problem of interpretation.

Analysis of possible solutions.)


In former articles, I both wrote about different aspects of this problem and discussed practical means to build an acceptable replica of the instrument. My aim is to deal not only with organological and technical subjects but to examine musical ideas connected to them, the way Music was considered both as an art and as part of the mathematical knowledge of Nature, since Pythagoras to the Middle Ages and further.


Several researchers have already carefully studied the few witnesses related to this instrument. I am not going to repeat the whole list, I just want to offer a short survey here.

We can find many features common to all specimens: the soundbox, consisting, as usual, of two oval/circular parts plus the neck, three strings are stretched along this body, then a keyboard showing 6 to 8 keys within the half of the diapason, sound holes are often in a D shape. The keyboard mechanism is depicted only once, in an 18th-century copy (Gerbert) of a 13th c. deperditum  manuscript: 8 revolving keys and the list of the notes, from C to c (including Bb and B) are clearly visible.  This drawing tells us clearly that one of the strings, (maybe all the three strings) was in C and that the three strings were touched by each key at the same time following a diatonic scale.

The six letters on the right compose the word magada (latin but having greek origins) written at the right place, around the wheel and the bridge. (In musical treatises, i.e. the manuscript containing the most famous Ad organum faciendum in Biblioteca Ambrosiana, Milan, XI c., magada is the name given to the bridges of the monochord)


Another well known 13th-century manuscript entitled “Quomodo organistrum construatur” illustrates the method to divide the monochord into the eight stops of a diatonic scale starting from Ut, but we don't find a description of the instrument nor information about its use. Scholars guess it was played mainly for sacred music along the 12th century. Christopher Page, the only one who faced the problem of the name: Symhonia / Organistrum, has several doubts about and no definite answers.


We know that almost all depictions and witnesses belong to the 12th century, but the year and the decade are mainly unknown. Since it is impossible to follow an exact chronology we cannot pretend to outline the evolution of this instrument. To study carefully the observable features is the only serious way to face the subject.

In Ahedo de  Butron (Burgos) sculpture, one of the musicians might be turning a crank with his right hand, while with his left-hand forefinger he is actually touching the second string of five; the second musician is touching the third string with his right-hand forefinger and with the other hand is turning the corresponding tuning peg. 


Hortus deliciarum


There is no evidence of a keyboard  in Hortus deliciarum manuscript. In Ahedo, since there is no trace of both crank and wheel, possibly the two musicians are either just tuning a long size Viella or tuning an Organistrum with no keyboard:

Soria Ahedo de Butron

In Soria sculpture (Spain) we observe only one string (?), no bridge, no wheel, no keys. The musicians look as they were actually turning a wheel and pulling the keys, but the damages suffered by this sculpture do preclude a clear observation of details. On the contrary, the similarly shaped instrument in Boscherville capital (France) presents crank, tailpiece, wheel, and keys.

Bosh Boscherville

What was this wheel intended to do, but to produce a continuous sound? This is the first observation with musical relevance in our description. Now, suppose we have built a long size Viella, about twice the size of a usual one, with a wheel in it: one of the two musicians can stop the strings all along the neck with his fingers, but he is not at ease cause his fingers interfere accidentally with the other strings. This is why a system of keys might have been suggested. In some depictions they appear, 6 to 8 within half of the diapason. They look like flat bars passing beneath the strings (Boscherville and Vercelli) or we can see the top of them protruding from the lid that hides the inner mechanism. That these keyboards were designed for a diatonic scale is out of doubt. The question is: were the bars equipped with tangents in order to operate on one string only or more than one?

According to Gerbert’s drawing, all  keys are acting on the three strings simultaneously in order to play a simple melody on the  three strings tuned at the same pitch. No other useful information is offered by the drawing : no indication of drones, no alternative tunings.

Eventually, if we want to extend the c scale, we should tune the lateral strings in c, the middle one  in c'. Then, by lifting the middle string and then the two laterals, (this task carried out by the man in charge of turning the wheel) we can obtain two full octaves.



As we assume that the instrument served to sacred music only, no use of drones have to be admitted, according to western tradition (although many scholars nowadays, influenced by byzantine fashion, perform  gregorian chants also adding drones) 



During the XII century benedictine monks were developing a new technique in polyphonic singing:  

the vox organalis was no longer in parallelum, dismitting the teaching of Musica enchiriadis and Micrologus,  and became freer. 

What was the new instrument role in that new music fashion?

To play the tenor part in organum melismaticum or floridum  for instance, as a ground reference for the upper voice.

A similar role (and similar limits as well) would pertain to the romanesque pipe organ (see J.Ferrando's article in: L'instrumentarium du Moyen Age. Paris, L'Harmattan,2015). 

The geographic area includes Spain and France mainly, then England, Germany, and Italy



At the top of the Gate of Glory in Santiago de Compostela cathedral magister Mateus sculpted a wheel instrument in the middle of the range of the 24 Elders of Apocalypse all around the Lamb. This gate is dated precisely the year 1188. This specimen differs from all others we have examined

  1. In its general shape
  2. In quantity and quality of decorations
  3. Having 11 keys within the octave.

The soundbox consists of two perfect circles connected through lobes and a rectangular box containing the keys. The string length is equal to the circumference of circles. Four triangular sound holes with little holes at the edges are cut in the first circle. A large quadripartite rosette with vegetable decoration is carved in the second circle. An interlace decoration made of 11 knots and 12 spaces is cut all along the rectangular keyboard lid.

Some of these features are unique among all depictions of the instrument. In other articles, I examined these characteristics in the light of musical theory, astronomy, and cosmology of the time. In the present paper I would like to focus on the interpretation of the keyboard with 11 keys within the octave, describing a possible reconstruction of it.

Many important scholars believe that this number indicates a chromatic division of the keyboard. Although they are aware of the fact that no chromatic scale was in use in the 12th-century music, they accept as a piece of absolute evidence that this abnormal chromatic keyboard was used for transposition. This is absurd because no full transposition of any melodic line spanning one octave at least can be made within a single octave! 

My idea is that this setting of keys could be only apparently chromatic and might serve a diatonic scale, this way: two lateral bass strings (a), middle treble string (a') whose nut lies a semitone behind the other two. This pattern works only with this tuning, enlarging Gerbert diatonic scale two tones under the c and reaching the g' of the second octave, including all useful notes of tenor parts in XII century organum melismaticum.

Please look at the next picture: notice the first octave blue (no flat here), the second octave red (chance on 8th bar only between e first octave and f second octave obtained by turning 90° the cilindric bar)



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This report gives rise to more doubts than certainties.

Santiago instrument appears to be the more complicated version of a wheel instrument documented for few decades during the 12th century, whose main relevance was due primarily to the continuous sound produced by the wheel, secondarily to the keyboard mechanism. 

We know nothing about the wheel and we assume it was a wooden one with rosin on it. Then we don't know whether the performer used to lift any of the strings from the wheel occasionally or not.

We ignore both the tuning and the keyboard mechanism in detail. It is possible that different solutions have been adopted here and there in different moments and places, including a simpler version with no keyboard at all.

At the beginning of  the XIII century the instrument disappeared.  Wheel instruments survived into smaller forms, playable by one performer, being equipped with a more practical  keyboard, to serve secular music.



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