Scambi (Exchanges) is an electronic music composition by the Belgian composer Henri Pousseur, realized in 1957 at the Studio di fonologia musicale di Radio Milano.


Scambi is Pousseur's second electronic-music work, following Seismogramme I–II (Seismograms I–II)—one of the seven works which had been presented in October 1954 on the first concert of full-scale compositions produced in the Electronic-Music Studio of the NWDR. Pousseur at this time had obligations as a schoolteacher in Malmedy and so could only come intermittently to work in the Cologne studio, where his friend Karlheinz Stockhausen helped carry out the technical realisation (Grant 2001, 75; Morawska-Büngeler 1988, 15, 109). His work on Scambi by contrast brought him into direct contact with the work of actually realising electronic music.

In the summer of 1956, at the Darmstädter Ferienkurse, Pousseur met Luciano Berio, who invited him to come to Milan to work at the Studio di fonologia musicale of Radio Milan. On his way to Milan on the train in the spring of 1957, Pousseur formulated two goals for his new work. First, he wanted to design the work in a way that permitted the listener to participate in its temporal formation, which meant it would be composed of a number of small elements which could be arranged in different ways. Second, it seemed necessary at that time to use material that avoided the periodic character of traditional music, including the internal structure of the sounds themselves. This meant starting from noise—white noise—and filtering it to produce a range of noisy sounds with different degrees of relative pitch. This came as an extension of the post-Webernian goal of exploring structures opposed to traditional ones, especially in the area of harmony, so that, in place of the concepts of polarity and causality of traditional musical thinking, "Es soll alles schweben" (everything should remain in suspension), as Webern put it (Pousseur 2004, 147–48; Pousseur 2005, 4).

A third factor preoccupied Pousseur: the time available to carry out the work was relatively short. Consequently, it was necessary to find relatively quick methods for the generation and formation of the material. This was an important factor in deciding on techniques that deviated from the microstructural devices accepted almost exclusively in electronic composition until the present time (Pousseur 2004, 148).

At the Studio di fonologia, Pousseur discovered a special filter designed by Dr Alfredo Lietti, the technical director of the studio. This device enabled selecting, by setting the filter's threshold, material from a complex sound phenomenon, or the opposite, progressively increasing the attenuation. In other words, various more or less dense "skimmed off" bandwidths can be isolated from the same stockpile of sounds. Studio technician Marino Zuccheri assisted Pousseur in compiling a supply of suitable sounds for his composition (Pousseur 2004, 147, 150–51).


The starting-point for Scambi is a collection of sound material that is globally statistical. By means of devices that enable transformation techniques, elements are selected from electronically generated white noise. Various frequency bands were isolated, each with a bandwidth of half an octave, and from each of these a sequence is filtered using an amplitude selector. The output is randomly determined by whichever sounds happen to emerge above the filter’s threshold. These sequences, which already fluctuate in frequency around average values, are then made to centre on nine different pitch levels. On each one, a directed motion of change in density is imposed in which the direction is not linear, but rather travels in a spiral fashion. An acceleration machine is then used to give each sequence a rising or falling pitch tendency, within which the motion is not even, but is disturbed by small internal deviations in contrary directions. This material is then reduced to four basic structural types, each characterised by a double tendency: on the one hand, movement from high to low or from low to high, and on the other from fast to slow, or from slow to fast (Sabbe 1977, 172–73).

Rhythms, too, are intentionally irregular and unpredictable. Details of the music are therefore "imprecise". On the whole, only general motions are heard—general speeds or changes of speeds—with abrupt breaks occurring even within these tendencies (Wilkinson 1958, 45).

A second structural level opposes this essentially discontinuous material with contrasting, long-sustained, continuous sounds, again in four types of shape. These two four-fold classes of structures are blended in various degrees to produce sixteen intermodulated structural types. Together with their retrogrades, a total of thirty-two sequences are generated: high-fast-discontinuous changing to high-slow-continuous, low-slow-discontinuous changing to low-fast-continuous, high -fast discontinuous changing to high-slow-discontinuous, and so on (Sabbe 1977, 173–74).

Once having produced these thirty-two sequences, Pousseur regarded the work as complete, though with an enormous number of possible realisations—an aleatory principle which had been intended from the outset (Pousseur 2004, 157).

Scambi is unusual for an electronic work in having a mobile structure. It consists of sixteen pairs of segments (called "layers" by Pousseur) that may be assembled in many different ways. Pousseur's original idea was to supply these layers on separate reels of tape, so that the listener could assemble his own version. When first created, several different versions were realized, two by Luciano Berio, one by Marc Wilkinson, and two by the composer himself—a longer one of about six-and-a-half minutes and a shorter one lasting just over four minutes. One of Berio's versions is shorter still at 3:25 (Pousseur 2005, 1; Sabbe 1977, 175n86). Pousseur established two principles for linking the segments together. The first is that there should be as complete a conformity in character as possible between the end of one segment and the beginning of the next, with the objective of accomplishing transitions as imperceptible as possible. The second is that the formal course should be marked by the successive dominance of the different characters. The process of assembly was complicated by the fact that the sequences were not all the same length, but it was not required that all thirty-two segments necessarily appear in all versions. Though Pousseur followed these rules himself, he regarded them only as suggestions, and Berio and Wilkinson did not conform to them when making their versions. Berio's structures, for example, are marked by an even distribution of the various characters, while Wilkinson's connections emphasize effects of contrast (Pousseur 2004, 157–58; Pousseur 2005, 18; Sabbe 1977, 175).


Initially, Scambi was not met with universal acclaim, even within Pousseur's immediate circle of colleagues. Pierre Boulez attended a concert of electronic music from Milan, given at Darmstadt on 26 July 1957, in which two versions of Scambi were presented, along with Mutazione and Perspectives by Luciano Berio and Notturno by Bruno Maderna. In a letter to his friend Stockhausen, Boulez reported:

I also heard the electronic pieces from Milan. What a catastrophe. The one by Pousseur is absolutely zero, both in the choice of material and in its compositional structure. And then, the white noise at a high level and with glissandos, which might be used for sound effects of storms... and these sorts of vaguely aquatic gurglings, and worse (just like a toilet), I find it abominable! (Boulez 2001, 180)

In his influential early book Opera aperta, Umberto Eco, on the other hand, cites Scambi, together with Stockhausen's Klavierstück XI, Berio's Sequenza I, and Boulez's Third Piano Sonata, as musical exemplars of the "open work", alongside the literary models of Verlaine's Art Poétique, Kafka's The Trial and The Castle, and James Joyce's Ulysses and Finnegans Wake (Eco 1987, 1–2, 8–10). For Eco, Scambi represents a "fresh advance" by pointing within the category of "open" works to a narrower category of "works in movement" consisting of "unplanned or physically incomplete structural units", related to products of visual art like Alexander Calder's mobiles and Mallarmé's Livre (Eco 1987, 12–13). It is evident from the vocabulary used by Eco that it is Pousseur's work that had the greatest impact on his thinking (Grant 2001, 177). Scambi was the first open-form work of electronic music—a mobile of electronic sounds (Volborth-Danys and Pousseur 1989, 42).


Beginning in 2004, the Scambi Project, directed by John Dack at the Lansdown Centre for Electronic Arts at Middlesex University, has focussed on this work and its multiple possibilities for realization.



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