published by "Organised Sound" Vol.8 / 2, Cambridge University Press, January 2004

Sound - Time - Space - Movement
The Space-soundInstallations of the Artist-couple <sabine schäfer // joachim krebs>

<sabine schäfer // joachim krebs>

Abstract, Introduction, afterword and translation:
Ralf Nuhn and John Dack
Lansdown Centre for Electronic Arts, Middlesex University London


This article describes the theories and practices of the German installation artists and composers Sabine Schäfer and Joachim Krebs. Much of their work concerns site-specific sound installations involving the articulation of time and space. Their principal work methods and materials are described. In addition, they have formulated a typology of five installation types which they describe using their own installations as examples. Each installation type responds to a particular set of aesthetic and practical challenges both for the artists and the visitors. These are discussed and illustrated in the article. The typology extends beyond the specific work of these artists and can be applied to installations in general thus providing a framework for critical analysis. Furthermore, the translators have discussed the issues regarding the specialised vocabulary of the artists and the rendering of such language into English.


The term 'installation' includes many different types of artwork. Some works are site-specific and derive their meaning from being placed in a specific location with historical, social or environmental associations. Others occupy a space within a gallery or public venue and function in a manner independent of the space itself. In addition to the physical dimensions, structure and position of the installation, the relationship between the aural and visual components is usually of fundamental importance. Both senses can provide mutual support or contradict each other in a series of constantly shifting and occasionally unsettling interactions.
In installations where sound is essential to the work, the sensibilities of musicians can assume a significant role. Working with sound is not, of course, the sole prerogative of musicians. Nevertheless, in general musicians are acutely aware both of the potential of real-world sounds as well as the acoustic properties of spaces. (This is particularly true of practitioners of electroacoustic music).
In recent works of the artist-couple <sabine schäfer // joachim krebs> spaces are 'sonified' by means of carefully constructed installations which are placed with meticulous care within the location. The physical arrangement of the loudspeakers becomes in effect a living 'body' or 'organism' creating a form of mediation between the sound types, their actual movements and the installation situated in the space. The static, physical structure is thereby 'energised' by means of computer control via specially designed software and the visitor experiences processes of revealing and exploring spaces by sound.

In the following article <sabine schäfer // joachim krebs> suggest a typology of installation artworks. Each type exemplifies a particular aspect of their practice and reveals a preoccupation for creating the most appropriate installation for the specific space and how it will be experienced by visitors. The value of such an installation-typology results not only from the way it explains the artist-couple's practice, but also from the more generally applicable criteria it offers other artists. Many installations can be situated within one of the suggested five types. Texts which comment upon and clarify artworks often have a particular authority if written by the artists themselves. Some artists, of course, are reluctant to explain their practice believing the work to be autonomous and capable of speaking for itself. However, when artists are willing to discuss their work, readers have access to the kind of private self-reflection that can be so illuminating.

In translating the article we encountered problems common to all attempts at rendering foreign texts into English. These concern not only issues of selecting the correct English equivalent but also the necessity of communicating accurately the writer's thoughts. For example, should a translator endeavour to retain the 'feel' of the original text? Such a decision might demand the retention of phrases which appear ungainly in English but nonetheless communicate something of the text's meaning. Many translators of Adorno, for example, seem to adopt this strategy. Sub-clauses are interposed between an introductory phrase and the main clause with its verbs at the end of the sentence. The English translation thus remains defiantly 'Germanic' in structure but, far from making the text opaque, the accurate placing of stress is preserved and meaning often enhanced. Alternatively, a 'free' approach can be adopted and the immediate comprehension for the reader - both specialist and non-specialist - is given priority. However, clarity can lapse into the simplistic and intelligibility suffers. Our solution is, inevitably perhaps, a compromise.

We have previously translated an article by <sabine schäfer // joachim krebs> describing the work 'Sonic Lines n' Rooms' (SAN Diffusion, Sept. 2000). In this article the artist-couple outlined their approach to the particular problems of this site-specific work (see also: Mitteilungen 33 of DEGEM, July, 1999 and Positionen 37, Berlin, November 1998). It was apparent that two terms required particular attention. The issue stemmed from the way two specific installation-types functioned. On the one hand, a 'sound-body' could be situated within a space and visitors are encouraged to approach it from various directions. Or, a 'sound-body' could be constructed such that people can move around within its confines. In the former case the visitor is external to the object, in the latter s/he is embraced by it. The German word describing an installation in which the visitor moves around in order to explore the interactions between the space and the sounds is 'begehbar'. This is the third installation-type, the 'enterable Space-soundBody' (begehbarer RaumklangKörper). In our first translation 'begehbar' was translated as 'accessible' but in the context of the present translation this word seemed imprecise. 'Accessible' suggests that the installation comprising the sound-body and the space in which it is situated is available to the visitor if s/he chooses to participate. In the present translation the term 'enterable' has been substituted for 'accessible'. Even though it is a relatively uncommon word, it conveys more accurately the necessity for the visitor to actually enter the installation and actively explore.
By contrast, the German term 'umgehbar', used for the second installation-type, indicates that the visitor can walk around rather than within the installation. The term we use is 'circumambulatory' as in 'circumambulatory Space-soundBody' (umgehbarer RaumklangKörper). This word is almost certain to be more familiar than 'enterable' and, as anyone with even a modicum of Latin will realise, it means that the installation can be walked around and approached from any direction (unless deliberately restricted by the artist). Naturally, it would have been gratifying to use words retaining the parallel construction of the German 'umgehbar/begehbar'. Circumambulatory/intra-ambulatory was considered (albeit briefly) but rejected as too unwieldy. In neither case is there any compulsion for the visitor to walk across the space in a straight line or around the installation in any direction - clockwise or anti-clockwise. Nor is movement meant to be uninterrupted. The visitor should, indeed must, make use of the complete space available to experience the animating effects of the sounds emanating from what appears to be a living 'sound-body'. The organic metaphor of a "sound-body" is deliberate.
The term 'Space-soundBody' (RaumklangKörper) - which must be differentiated from 'Space-soundObject' (RaumklangObjekt) - has been retained in English. Consequently, we were persuaded to translate its separate components or 'Glieder' as 'limbs' to maintain the organic metaphor rather than use the more neutral word 'parts'.

Lastly, we should not overlook the playful aspect of artists' language. In the description of their work 'TopophonicPlateaux' <sabine schäfer // joachim krebs> use the term 'Klangfarbgrundierungen'. The play between the words 'Farbe' (colour) and 'Grundierung' (a painter's 'priming coat') is lost unless the term 'Klangfarbe' - literally 'sound-' or tone-colour' - is understood. However, to express the concept of a first step which is needed before the final application of other sounds, our translation as 'sound-colour priming coats' communicates (we hope) the idea accurately (though unfortunately not with the lightness of the original text). Such are the problems of translation and we can only hope we have captured the essence of what these artists wish to express.

by <sabine schäfer // joachim krebs>

I. Time Becomes Space - Space Becomes Time

All modern perception theories are based on the fact that human perceptions of time and space are interdependent. A distance covered by a person - or a sound - in space is initially perceived as a temporal phenomenon, allowing a person to develop a subjective notion of space and time by measurement and comparison.
Thus, movement in space becomes time. Time periods become spatial distances. The sensation of time is realised by the sensation of space and vice-versa. Space becomes an experience of time due to the movement of the sound event. Time accordingly becomes an open, imaginary process of generating illusory space. Rooms which are open, unbounded, liberated from the linearly directed flow of time serve as three dimensional canvases for constantly changing processes generating transitions.

Between TemporalSpaces and SpatialTimes, there are manifold variations of IntermediateZones with their IntermediateSpaces and their IntermediateTimes.
All this leads to a dissolution of the real performing space, where time itself stages a linear-dramatic, goal-directed idea (of space?).
Instead, the cyclic, non-linear consciousness of time releases the desire to become "immersed" in psychological inner space, to fade out physical outer space with its real time and its thinking spaces (which are predetermined in their substance) by concentrating on the perception of what might seem on the surface, unprepossessing sound events based on elementary-harmonic, simple sound-materials and -transformations, to set free your vision, or to put it better, your hearing, so that you may experience the present - from one moment to another - as a possibility of transitions, of freely flowing conditions.

In the Space-soundInstallations of the artist-couple <sabine schäfer//joachim krebs> specific soundspaces are created, which incorporate the movement of sounds in space as an intrinsic part of the composition. The composition's individual sound strata are, so to speak, transferred into the exterior space and by means of a loudspeaker matrix - which is installed in the space and controlled by computer with software exclusively developed for the artist-couple - moved and placed respectively in space. Hence, the free distribution of sound sources in space and the compositional sound space extended by the real movements of sounds, are specific to this space-sound art. This compositional sound space - primarily defined as time-based art - thus also approaches spatial art. This is comparable with the medium of film/video, in which the image formerly represented statically can, by its movement, be experienced as time-based art.

The experience of space-sound events which are moved in the architechtonic space is not only meant to give an intensive spatial experience, it also becomes an experience of shaping time acoustically and artistically.
Individual sound locations and sound sources are, by their movement, turned into a quasi organically proliferating sound line, which - itself interconnected to build an artificial matrix of time and space - offers acoustic images of SpaceTimeNets floating freely in 'non-time'.
Space and time themselves are turned into interactive qualities of perception, constantly fluctuating between the 'real' and the 'unreal' sensation of space and time.

II. Artificial Soundscapes between Pure Realism and Pure Abstraction

In almost all works of the artist-couple from 1995 onwards in the area of Space-soundInstallations, amorphous animal/natural voices and sounds respectively, as well as heterogeneous everyday noises from human surroundings and habitats form the most important sonic source material, though there is neither language, singing nor instrumentally or synthetically generated sound material! Below are examples of the most essential aspects of the artist-couple's working methods.

An initial, important stage in composition is the intensive study of each individual found and selected noise and sound. The most important question at this stage is: which naturally existing and which potential, artificial consistency is held by each individual sound in the initially inaudible, molecular interior of its microstructure? Therefore, noises and sounds are recorded with a digital sampler. Delving into the smallest molecular region, the sampler is able to put at the disposal of the sound artist single particles of the inner structure of this noise-sound matter for artistic development. With these 'abstract machines' - to quote a concept of the French philosophers Deleuze/Guattari - we carried out, as it were, what we called an 'EndoSonoScopy' of the individual sound materials to take single sound tests (so-called samples or fragment-patterns) from the organic sound web. Here the samplers serve as audio-microscopes with a complex of interfaces, which enter the organic sound structure in order to record and split their variations into molecules. These are then artistically transformed in a further operation.
Previously imperceptible inner-polyphonies and harmonic sound-fields of unfolding inner resonance spaces now become audible. What occurs is, as it were, a revealing and exteriorising of the inner intensities of the respective sounds.
All of this was 'preparatory' work carried out according to a quasi scientific approach of the observer and researcher; only now does it become interesting for the actual artistic composition process. The next stage is to produce an artificial consistency by means of the most varied artificial transformations of the previously carefully selected sound materials.

The artificial consistency formation as a symbiotically-fluorescing 'animal-nature-noise- becoming' of sound succeeds here all the more when the animal, nature, noise becomes something 'other': pure line, pure colour, pure rhythm, pure movement, pure figure… pure condition.

Furthermore, so-called 'artificial sound milieux' are formed in a quasi acoustic amalgamation process. That is, a temporarily existing, specific mixture of sound substances and particles creates a symbiotic diversity of dynamically driven SoundEnergyStructures by means of self-impelled, proliferating self-intensifying loops - always starting from the middle (mi/middle lieu/place).

Another essential aspect of this microscopy of sound and noise is the dissolving of each particular sound's semantic meaning. Whereas, at its original pitch, the sound was identifiable as something 'definite', for example a frog or a toad, it moves further away from its original semantic character the stronger the augmentation degree is. One could also say that the subjective substantial matter of the original sound transforms into a desubjectivised expressive matter of transformed fragment patterns. Intermediary stages during changing consistencies are formed, between concrete and abstract, natural and artificial and so on.
Thus, the artificial soundscape appears as an ensemble of desubjectivised expressive matter in the artistically layered sound system of the horizontal, rhythmic-melodic sound figure and the vertical, resonant-harmonic sound-space.

III. The five most important types of Space-soundInstallations

Over several years different types of Space-soundInstallations have crystallised and developed - due to, amongst other things, different performance situations. The five most important types will be illustrated below:

    1. The Space-soundObject
    2. The circumambulatory Space-soundBody
    3. The enterable Space-soundBody
    4. Space-within-Space
    5. Concert Space-soundBody

1. The Space-soundObject

Fig.1 SonicLines The characteristic aspect of the Space-soundObject is a two-dimensional arrangement of the loudspeakers, which radiate sound in one direction. This results in an optimal reception zone in which the visitor can approach and move away from the object. Therefore, Space-soundObjects are usually positioned against a wall.
Figure 1 shows the Space-soundObject 'Sonic Lines', commissioned by Nuova Consonanza, Rome in 1998. The 2-dimensional loudspeaker configuration is placed in the shape of an 8-limbed line alongside a marble wall in the foyer of the Goethe Institute in Rome. The loudspeaker configuration of the Space-soundObject is inspired by the specific dimensions of the architectural space. Clearly perceptible 'line-sounds' (forming rolling-ball motifs) are counterpointed by internally fluctuating water sounds which represent the liquid, unstable condition of the 8-channel Space-soundComposition.

Fig.2 Hörbild (Audible Picture) Figure 2 shows the Space-soundObject 'Hörbild' ('Audible Picture'). The eleven-limbed speaker ensemble is set into a monochrome, blue sound-wall, resulting in an object resembling an image on a panel. The speaker matrix of the 'Hörbild' forms the shape of an infinity symbol.
However, the sound does not only move along the path of the infinite bow, but the speaker tableau becomes instead a territory, a construction for sounds on which they spread, compress, evaporate and become solid again. The Space-soundObject was commissioned by the Siemens Arts Program, Munich and was presented for the first time at the Berliner Festwochen 1995 with the 11-channel Space-soundComposition 'Tableau I-III'. Further works were produced in 1997 for the first exhibition of the Sender Freies Berlin (SFB) sound gallery and for the MusikTriennale Cologne 1997, commissioned by the Studio Akustische Kunst of the WDR (Klaus Schöning).

2. The circumambulatory Space-soundBody

The circumambulatory Space-soundBody is a type of Space-soundInstallation the individual exhibits of which have a three dimensional sculptural structure of loudspeakers which can radiate sound in different directions and which is specifically developed for the particular architectural space. The distribution of the sound sources in the space is arranged in such a way that both a horizontal and a vertical linear loudspeaker body are formed, around which one can walk and through which the individual sound strata sound with specifically developed types of movements.

Fig.3  Space-sound Body 1 from Sonic Lines n´RoomsThe dimensions, and measurements of the individual loudspeaker-body depend on the size of the performance space. As required, an object is developed for the loudspeaker ensemble on which the loudspeakers are installed, as shown in figures 3 and 4.

As the loudspeakers can radiate in different directions and the loudspeaker ensemble is free-standing in the space, the visitor can - by contrast with the Space-soundObject - perceive the sound from different directions, the term 'circumambulatory' primarily refers to the three-dimensional reception mode of the variable listening perspectives, which are of equal quality throughout the entire space.

Fig.4  Space-sound Body 2 from Sonic Lines n´RoomsThe two examples illustrated here from the project series 'Sonic Lines n'Rooms' represent an 8-limbed 'diagonal-horizontal' (Fig. 3) as well as an 8-limbed 'diagonal-vertical' (Fig. 4), circumambulatory Space-soundBody. The loudspeakers are installed on steel crossbeams - each approximately 10 metres long - running across the space. The figures show two of the four rooms of the vaulted cellars of the Fürstlich Fürstenbergischen Hofbibliothek, for which the artist-couple created a four-part Space-soundInstallation, as a commissioned piece for the Donaueschinger Musiktage 1999.


3. The enterable Space-soundBody

The characteristic aspect of the enterable Space-soundBody is the artistic-poetic treatment of the architectural space. This is initiated by the artificial transformation of the raw material 'space at location' in order to open up the composed sound space by means of the three-dimensional movement of the sounds and to facilitate specific states in the acoustic becoming of architectural space.

The loudspeaker configuration of an enterable Space-soundBody almost always includes the entire architectural space. Generally, the speakers are positioned around and close to the walls on different levels so the visitor - surrounded by the loudspeaker body - can move freely within the space in order to experience very different auditory perspectives.
The result is specific sound spaces which are, among other things, shaped by the special characteristics of the particular architecture. What takes place is in effect an 'acoustic topographing', so that the dimensions of the imaginary auditory space and the real 'sounding' sound space interweave and create a state of a specific space-time-continuum.
Through the aspect of permanence these states preserve a certain authenticity of the 'real' in their being-/staying-the-same and their constantly varied repetition.

For the recipient, real space and moved sound space create specific synergies. The illusory space of imagination develops (through the moved sound and one's own movement) within the real space. What happens here is, so to speak, the cancellation of the 'real' boundaries of space. Mental processes of changing location are initiated, which - though imaginary and removed - are evoked by means of the shaped 'real' location with its corresponding sound architecture.
A specific space emerges in order that perception itself becomes specific.

Fig.5  Space-sound Body 3 from Sonic Lines n´RoomsThe enterable Space-soundBodies shown in figures 5 and 6, represent another component of the aforementioned 4-part Space-soundInstallation project 'Sonic Lines n'Rooms'.
The four-part ensemble as a whole - with a 32-channel Space-soundComposition for 4 x 8 loudspeakers - is the artist-couple's first production for the project series of the same name: 'Sonic Lines n'Rooms'. The series links the two different types of Space-soundInstallations 'circumambulatory Space-soundBody' and 'enterable Space-soundBody', which are - depending on the project -applied individually or in combination.

Fig.6  Space-sound Body 4 from Sonic Lines n´RoomsThe Space-soundBody 3 from 'Sonic Lines n'Rooms' was premiered in 2000 as a separate enterable Space-soundBody at the 'KlangArt Buch', organised by the Akademie der Künste Berlin. The concert performance of the Space-soundComposition 'Sonic Lines n'Rooms No.3' took place in the same year in Rotterdam, the Netherlands, as part of the 'v_2' series of events 'Time-Based Space'.
The Space-soundBody 4 from 'Sonic Lines n'Rooms' was first presented separately as part of the MIX.01 festival in Aarhus, Denmark in 2001 and the Space-soundComposition 'Sonic Lines n'Rooms No.4' was premiered as part of the 10th Florida Electroacoustic Music Festival in Gainesville, USA.

There are of course manifold hybrid forms of the three described types of space-sound installations (Space-soundObject, circumambulatory and enterable Space-soundBody) of which two possibilities are introduced in the following text.

A. Hybrid form of enterable and circumambulatory Space-soundBody with Space-soundObject.

Fig.7  LOSTThe 18-limbed Space-soundInstallation LOST (Fig 7) was staged with lighting and was created for rooms with high ceilings and long reverberation periods. It was first exhibited in 1992 in the light-well of the Badischer Kunstverein in collaboration with the ZKM (Centre for Art and Media) in Karlsruhe, Germany. The Space-soundInstallation is, above all, characterised by an approximately 7m high, 6-limbed loudspeaker column (Fig. 7, level A). Sound-masses plunge down over this Space-soundObject and pull themselves up again in specific phases.

When entering the space through the gallery in the upper floor the visitor is occasionally surrounded by a band of sound that moves across an enterable Space-soundBody in the shape of a 6-limbed loudspeaker-semicircle (Fig. 7, level B) and counterpoints the plunging sound gestures. The circumambulatory Space-soundBody of level C, which is positioned on the floor, mainly transmits fluctuating sound-colour priming coats ('Klangfarbgrundierungen') and forms the sound tableau for the moved sounds of levels A and B.

B. Hybrid form of enterable Space-soundBody with two circumambulatory Space-soundBodies

The 28-limbed Space-soundInstallation 'TopophonicPlateaux' (Fig. 8) which is staged with lighting consists of a 27-limbed loudspeaker ensemble with a computer controlled concert grand piano. The 28-channel Space-soundComposition was designed as a commission by the Donaueschinger Musiktage 1995, specifically for the Sternensaal concert hall in Donaueschingen, Germany. This Space-soundBody is characterised by three installation components (see Figure 8).

Component 1: An outer circle - consisting of 15 loudspeakers - which starts at the right edge of the stage and ends at the left edge. The loudspeakers are positioned at heights which successively ascend and then descend again. The computer-controlled grand piano is located on the stage and thus, as the 16th limb, it completes the space-enclosing loudspeaker circle. The grand piano is triggered in real-time and is synchronised with the loudspeaker ensemble via the computer.
Fig.8 TopoPhonicPlateauxComponent 2: Two columns - each consisting of 4 loudspeakers -, which are positioned opposite each another in the inner space. The loudspeakers are staggered at different heights and radiate in different directions. The two loudspeaker-columns represent typical circumambulatory Space-soundBodies.
Component 3: Four loudspeakers, each of which is positioned on the floor in the corners of the space. This group of loudspeakers applies sound priming coats to the space and extends the loudspeaker circle described under component 1 to a 20-limbed enterable Space-soundBody.


4. Space-within-Space

This artistic concept is based on a self-contained enterable Space-soundBody as 'space within (architectural) space'. Consequently, the enterable Space-soundBody also becomes circumambulatory.
Through the combination of the features of circumambulation and enterability, new qualities emerge which establish an autonomous type of space-sound installation art. An example of this is the Space-soundBody 'Klangzelt' (Soundtent) from the project series 'SonicRooms' (Fig. 9).
Fig.9 SoundTent SonicRooms The architechtonic dimensions of the space surrounding the Space-soundBody itself is not explored acoustically - or to put it better 'sonified' - a process which would in a sense render the room itself 'audible'. On the contrary, the installation aims to eliminate as much as possible the real - visual as well as acoustical - environment of the place where the enterable Space-soundBody is installed - it is in fact a room within a room.

The interior of the Space-soundBody entitled 'Klangzelt' ('Sound Tent') which is easily and effectively separated from its surrounding space by a double fabric cover, leaves aside as much as possible the visual aspect of the artistic design of space and time to intensify the auditory reception of the artificially created virtual SoundSpaces.
As visual contact, a crucial premise for orientation and localization, is prevented by thin draping which is impervious to light but permeable to sound, it is possible to create unreal-imaginary 'SensorySonicRooms', where actual moved sounds - perceived only by the ear - can be experienced as an amorphous continuum of fleeting and intangible conditions and acoustic atmospheres.

Sound Tent SonicRoomsParadoxically, the artificial spatial qualities of sound are even enhanced by actual movement. So, in order to experience the 'Klangzelt' adequately, you have to be there 'live', so that you may, for example, experience the difference between artificially produced spatial qualities in the stereo image and the artificiality of psychological "inner" perception of space, which is evoked by sounds tracing the actual distance from loudspeaker to loudspeaker.
On the other hand, there are artificial 'listening islands', which - similar to listening with headphones - shut out the real space of the location by means of surrounding fabric covers, so that the artificially produced spatial qualities of the spatial sound compositions themselves will be more authentically perceived. Thus, at these islands it will also be possible to achieve new listening experiences, which, among other things, may lead to irritations of the 'normal' perceptions of space and time. In the best cases the sound artwork evokes a free flowing SpaceTime experience between an imaginary, psychological inner space and an 'actual' physical exterior space.


5. The concert Space-soundBody

The concert Space-soundBody represents a special kind of Space-soundInstallation. The most important criteria of this type of Space-soundInstallation, which focuses solely on sound, are:

An example is the Space-soundComposition 'TopoSonic Lines n'Rooms with Instruments' (from Spring 2002) for a 12-limbed Space-soundBody, experienced in concert form, with 8 loudspeakers and 4 instrumentalists (Percussion, Flute, Clarinet, Oboe).
As a commission for the AUDI-Culture Fund, this work has been tuned especially to the architecture of the 'museum mobile' in Ingoldstadt, Germany. To suit the circular performance space the loudspeakers and the instrumentalists, as shown in figure 10, were grouped around the seated audience. By means of a corresponding instrumentation, the instrumental part of the Space-soundComposition - in the same way as the digital 8-channel tape - takes into account aspects of the space-sound movement, resulting in a jointly 'acting' 12-limbed Space-soundBody.


by Ralf Nuhn and John Dack

There is, of course, no compulsion for artists ever to write about their practice. The histories of all the arts have bodies of artworks with little or no corroborating evidence from those who produced them. The theory is there, of course, but it is in the work and we must disentangle it if we choose to analyse the work. However, since the beginning of the last century and the institutionalisation of art there has been a marked increase in texts written by practising artists who want to (or feel obliged to) communicate the processes and underlying aesthetics of their work. These might be texts written to emphasise a personal role in an art-form's historical development - how many claim to have "invented" minimalism or conceptual art, for example? Other authors are deliberately polemical such as the young Boulez condemning as "useless" all those who failed to recognise the necessity of serialism. Some, due to their role as teachers theorise their practice within a pedagogical framework. For the theoretician or critic all these writings provide valuable source material. Any form of self reflection will almost certainly be appropriated by the academic community as an invaluable research resource. It is an important way in which intellectual and aesthetic discourses are created and sustained.

The sound installation categories of <sabine schäfer // joachim krebs> described in the article have been developed in the context of their own unique and original practice. The absence of references to other artists indicates neither unfamiliarity with the world of installation art, nor excessive introspection. As artists who write about their work, their principal responsibility in this article is to provide a coherent account of their own practice. Our role as translators is to render the text accurately into English. However, due to our close contact with the text and its authors, a secondary contextualising role has emerged. Once a typology has been suggested it is available to everyone and can be used with or without modifications to see if additional works can be included within its categories. Some will be placed easily, others will resist inclusion. Both results can be informative.

For example, the circumambulatory Space-soundBody (category 2) is, broadly speaking, identical to sound sculptures in general. Both terms refer to a three-dimensional object which can be walked around and which emits sounds in different directions. One could, therefore, place sound sculptures such as Stephan von Huene's Extended Schwitters (1987), Trimpin's Liquid Percussion (1991) and Rolf Julius' Zwei Steine (1999) in this category.
However, a clear distinction must be made. <sabine schäfer // joachim krebs> emphasise that, due to the use of multi-channel recordings and individual loudspeakers, the limbs of their Space-soundBody can emit different sounds. This use of specific sounds from each limb would differentiate their works from those cited (with the possible exception of Trimpin's Liquid Percussion). Nevertheless, this does not contradict the initial classification. The consideration of the specific role of sounds simply adds a further stage of refinement.
The first category - the Space-soundObject - can also be applied in this way. In this two-dimensional arrangement, sound is emitted in one direction. Similar examples are Takehisa Kosugi's Interspersions (1987) and Christina Kubisch's The True and the False (1992). In both these works small speakers are mounted on walls in plant-like configurations with the loudspeaker wires resembling stalks. The distinct character of each work depends, naturally, on the specific lighting, the position within the venue, the object's dimensions and (most importantly) the sounds used by the artists. By including these works in the category of Space-soundObject these individual features are not disregarded. The defining aspect of the category is still the directionality of the speakers and the restriction placed on the viewer's position. Additional examples can be suggested for the other categories.
As the enterable Space-soundBody (category 3) has loudspeakers placed on the walls of the space at various heights and positions, the visitor can move freely in order to experience different auditory perspectives. An obvious historical example would be the Philips Pavilion at the Brussel's World Fair in 1958. Though in this case the movement of the sounds and the accompanying images were more important than the "sonification" of the space as such. Other examples are Bernhard Leitner's Ton-Raum (1984) and Ryoji Ikeda's A (2000). In the latter case pure sinewaves and random noises were played within a narrow, purpose-built corridor. The acoustic properties of this, albeit simple, space created different listening experiences for the visitors. By walking at different speeds and by changing direction along the corridor, the visitor could locate and pass through distinct "sound areas".
Examples of the fourth category - Space-within-Space - are less common. This type is based on a self-contained enterable Space-soundBody within the confines of a gallery or a similar space. Consequently, such a Space-soundBody is also circumambulatory. Once again, a potential example can be found in the works of Bernhard Leitner. His Cylindre Sonore (1987) is a cylindrical space containing 24 loudspeakers. The sounds emitted are modified by natural factors such as temperature, humidity and light. Our sole reservation regarding this work as Space-within-Space is that is it situated in the open air rather than within a venue with clear, architecturally defined acoustic characteristics. However, the visitor to Leitner's space will experience both the sounds within the cylinder and the sounds from outside.
Finally, the five criteria of the final category - the concert Space-soundBody - conform to certain electroacoustic compositions where live instrumentalists play in conjunction with recorded sounds. Even though an exploration of the specific characteristics of the venue is not the principal objective, the practice of sound diffusion is necessarily influenced by the venue's acoustics. No electroacoustic composer would minimise the importance of this relationship which will, therefore, have a decisive effect on the work as a whole. For example, Stockhausen's Kontakte für elektronische Klänge, Klavier und Schlagzeug (1959-60) has a fixed form and audience-instrumentalist relationship. In addition, the use of four channel tape and the positioning of the loudspeakers and musicians will ensure the intimate connection between the electronic sounds, the live sounds and the concert space.

From these examples it is clear that the typology suggested by <sabine schäfer // joachim krebs> suits some works but needs modification for others. It must be stressed that this particular typology was the end result of the work and practice of <sabine schäfer // joachim krebs>. This is its unique quality and its strength. Had it been developed by a theoretician, musicologist or art historian the problematic nature of several of the aforementioned examples might well have been addressed by creating sub-categories. However, in our initial attempts the additional refinements usually resulted from considering the types of sounds and how they were used by the artist. This specificity was clarified by an initial categorisation. It is our opinion, therefore, that the origins of these five categories in the works of <sabine schäfer // joachim krebs> does not preclude their general applicability. The art of the sound installation is still relatively new and this typology is an important addition to its theoretical framework.