The period between Berlioz’ Symphonie fantastique and the end of World War I brought about a dramatic increase in orchestral means and ends, and in many musical areas a continuous development of what here has been referred to as idiomatic orchestral practice. In the music of composers such as Wagner, Mahler and Strauss on the one hand, and Rimsky-Korsakov, Stravinsky, Debussy and Ravel on the other, a wealth of new methods and mindsets emerged that form the focal point of the present discussion. This development has steadily continued, of course, if perhaps not with the same impact and speed. And although experimental music of the 20th century is not the topic of this book, it seems natural to comment on some of these innovations.
Innovation in idiomatic orchestral practice reveals itself not least in the use of vibrant fields of sound that technically represent a further development of the Strauss passages quoted above (figure 95, figure 103 and figure 104). Such mass effects are naturally linked to the medium of the orchestra (in the broadest sense) and its associated paradigms. Apart from keyboard instruments and certain percussion instruments, the concept of a “mass of sound” clearly entails the simultaneous activity of several or many instruments. After World War II, such effects often appear in the form of so-called clusters (i.e. closely adjacent notes), particularly with strings divided into numerous single parts. A cluster is basically an aggregate of pitches covering a specific range in which neither single notes nor separate parts of the cluster dominate.
A dense sound field, essentially consisting of all notes within a delineated area (sometimes referred to as frequency band) is harmonically anonymous, reminiscent of so-called “white noise,” a term designating a sound in which the entire frequency range of a particular bandwidth is represented with equal volume. The association to the color white (the combination of all colors) seems reasonable and suggests why such clusters frequently are used as a backdrop for foreground activity, not unlike the way in which colors and lines appear on a white canvas or piece of paper.
Here strings and brass each fill the space of an octave from low Bb to A in the form of a chromatic cluster. Strings apply sustained tremolo while the brass plays repeated notes with continuous, unsynchronized attacks. Ligeti clearly aims to keep each group balanced: horns are doubled two by two to balance with the brass in accordance with Rimsky-Korsakov’s balance ratios (cf. Chords). The sound field is passive, but the bustling activity provided by the brass attacks creates a sense of foreground and background.
In his work Apparitions (1960), written a year earlier, Ligeti had introduced a texture composed of a multitude of simultaneous lines that, like a thousand threads in a piece of fabric, merge to coalesce into a mass of sound (Ligeti himself described it as “micropolyphony”). These ingeniously woven textures are packed with detail, a microorganism of swarming movement that is perceived from a distance, resulting in a diffuse and static field of sound with internal movement. This innovative technique was further developed by Ligeti in his seminal work Atmosphères.
Beginning with the lowermost 2nd violin (No. 14), voices enter one by one. Constructed as a kind of canon, each part consists of a falling line, although in different rhythmic guises. The density of this myriad of monochromatic voices render the canon intangible, as the listener’s perception is not that of a canon, but a vibrating field of sound. Furthermore, the example given here is only one of several segments making up the total soundscape. With minor deviations, violas and cellos play an inversion two octaves below the canon in 1st and 2nd violins, while the double basses present a sustained chromatic eight-note cluster in the low register.
Witold Lutoslawski’s orchestral work Jeux vénitiens (1961) shows influences of John Cage’s notion of indeterminacy and “chance operations,” in Europe better known as aleatorism. Lutoslawski realized that limited, controlled randomness had the potential to liberate music from melodic and rhythmical details while at the same time maintaining full overall harmonic control. The borderline between vertical and horizontal, melody and harmony, is obscured without eliminating the idea of clearly defined harmonic structures as a vital principle. Disregarding the coordination between separate voices and a common pulse, Lutoslawski found a way of letting single melodic lines merge into harmonic fields characterized by melodic as well as rhythmic activity and movement. Controlled chance unfolds in flickering, coloristic fields supported by clearly perceptible chordal structures.
The music evolves in “ad libitum sections” in which all musicians play at the same tempo without being coordinated with one another. This is underlined by uncoordinated accelerandi in the individual parts. But everything else is strictly controlled: the sound field contains three notes (Eb, F and Bb), freely formed in each of the ten parts and – as in the example by Ligeti – gradually absorbed into a larger field consisting of all twelve notes in an octave from low Bb to A. Thus, the final sound field is a chromatic cluster, but characteristically results from the sum of diatonic motives. At an overall level, Lutoslawski controls the transition from motif to sound field by means of attacks and rests. Such ad libitum sections are not conducted, but indicated by the conductor at the beginning and end of a section (marked by a downward arrow).
This type of notation allows musicians a great deal of freedom in forming their own part, while the sum of many individual, uncoordinated voices creates a rhythmically vibrant field of sound whose harmony is under the full control of the composer.
In the example above, Lutoslawski combines ad libitum sections with so-called “spatial notation.” The individual voices remain independent of a common meter, strong and weak beats, etc., resulting in a music that is rhythmic but without a pulse. All five sopranos have glissandos from F# to C and from C# (Db) to D, and here, too, the sum of all melodies generates a field of sound. The visual distance between notes determines the rhythm and a caesura indicates a short rest. Singers repeat their parts until measure 60, unsynchronized with each other or with the orchestra. The conductor leads by marking a beat every second, the musicians reading the music according to a proportional timeline in which one measure equals one second. The duration of white notes in the vocal parts is given by their horizontal spacing in the timeline, while black notes are performed short, i.e. staccato.
The Polish composer Krzysztof Penderecki simplified the notation of his own music dramatically, almost to the point of stenography. While chromatic string clusters require precise notation of every single note by a composer such as Ligeti, Penderecki simplifies these by graphically indicating the width of the cluster, leaving it up to the music copyist to distribute the separate notes among individual players. Indicating unusual playing techniques intended to produce noise-like sounds by using simple symbols, the score becomes a schematic graphic representation of the sound process. The fact that it was possible to adapt traditional notation to entirely new purposes driven by purely practical concerns, simplicity and readability resulted in yet another contribution to the development of the orchestra (while addressing the perpetually tense relationship between ever new musical ideas and a notational system that had remained virtually unchanged for 400–500 years).
The conductor cues each individual entry using the timeline at the bottom of the page. The four string groups above are notated by means of instructions that indicate noise-like sounds without specifically defined pitches.
From a technical point of view, several of these examples produce mass effects by multiplying a single voice, for instance by displacing each part layer by layer in interval or time. The Greek-French composer Iannis Xenakis, however, was fascinated by what he called “sound galaxies,” masses of sound with constantly changing density, tone color and character. The myriads of single stars in a galaxy move in unpredictable ways, but the galaxy as such, its movement, appearance and luminosity may very well be predicted. To put it another way: when the number of single musical element reaches a certain threshold, they become individually insignificant and can be generated statistically by a computer, while the overall effect can be controlled by clearly defined intentions. Xenakis used the technical term stochastic (after Greek stochos = aim) to describe this method. It enabled him to compose using vast masses of sound, giving them a precise geometric and architectonic shape without laboriously having to compose every single note or rhythm in the texture. A piece of software could then easily translate these stochastic calculations into thousands of notes, none of which had any individual significance. While Ligeti and Lutoslawski achieved diversity through multiplication of a single unit, Xenakis did the opposite by targeting an infinite diversity and manipulating it as a single uniform entity. A possible first in musical history, Xenakis’ work Metastaseis (1954) is scored for 46 string players in which no two performers play the same part.
The cluster-like harmonic density and masses of sound made up of countless elements without individual significance make these examples decidedly different from the harmonically vibrating fields of sound or “accompaniment without melody” previously highlighted in the music of Debussy, Strauss, De Falla, Holst, Stravinsky and others. But essentially they share the same mindset. And the literature provides numerous examples of intermediate situations where dense sound structures superficially seem to contain activity while in fact consisting of static chords or harmonic fields of sound (a phenomenon comparable to ocean waves: the waves move, but the water does not).
Beginning in the mid-70s, the American “minimalists” – composers such as Steve Reich, Philip Glass and John Adams – wrote music that was extremely vertical, organized in tonal fields pushed forward by slow modulations and repetitive patterns of rhythm and melody, patterns gradually displaced in relation to one another, then finding new ways of conforming, only to be subjected to further displacement in a continuous, sustained process. Once again, the foundation is provided by a rhythmically pulsating sound field, only here built on tonal (if rarely functional) harmony rather than chromatic clusters. Even if chordal progressions are virtually absent, the previously introduced concept of “active harmony” is hardly an inappropriate description here.
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 The term “spatial notation,” also known as “proportional notation,” means that the music is notated in a coordinate system whose vertical axis represents pitch (here in traditional five-stave notation), while the horizontal axis represents time. In its most basic sense, traditional notation, too, can of course be seen as a type of coordinate system.