György Ligeti
From 1956 to Le Grand Macabre

Upon arriving in Cologne, Ligeti began to write electronic music alongside Karlheinz Stockhausen and Gottfried Michael Koenig at the electronic studio of West German Radio (WDR). He completed only two works in this medium, however—the pieces Glissandi (1957) and Artikulation (1958)—before returning to instrumental music. A third work, originally entitled Atmosphères but later known as Pièce électronique Nr. 3, was planned, but the technical limitations of the time prevented Ligeti from realizing it completely. It was finally realised in 1996 by the Dutch composers Kees Tazelaar and Johan van Kreij of the Institute of Sonology.

Ligeti's music appears to have been subsequently influenced by his electronic experiments, and many of the sounds he created resembled electronic textures. Ligeti coined the term " micropolyphony " to describe the texture of the second movement of Apparitions (1958–59) and Atmosphères (1961). This texture is a similar to that of polyphony, except that the polyphony is obscured in a dense and rich stack of pitches. Micropolyphony can be used to create the nearly static but slowly evolving works such as Atmosphères in which the individual instruments become hidden in a complex web of sound. According to Ligeti, after Apparitions and Atmosphères, he "became famous".

With Volumina (1961–62, revised 1966) for solo organ, Ligeti continued with clusters of notes, translated into blocks of sound. In this piece, Ligeti abandoned conventional music notation, instead using diagrams to represent general pitch areas, duration, and flurries of notes.

Poème symphonique (1962) is a work for one hundred mechanical metronomes during his brief acquaintance with Fluxus movement.

Aventures (1962), like its companion piece Nouvelles Aventures (1962–65), is a composition for three singers and instrumental septet, to a text (of Ligeti's own devising) that is without semantic meaning. In these pieces, each singer has five roles to play, exploring five areas of emotion, and they switch from one to the other so quickly and abruptly that all five areas are present throughout the piece.

Requiem (1963–65) is a work for soprano and mezzo-soprano soloists, twenty-part chorus (four each of soprano, mezzo-soprano, alto, tenor, and bass), and orchestra. Though, at about half an hour, it is the longest piece he had composed up to that point, Ligeti sets only about half of the Requiem 's traditional text: the " Introitus ", the " Kyrie " (a completely chromatic quasi- fugue, where the parts are a montage of melismatic, skipping micropolyphony), and the " Dies irae "—dividing the latter sequence into two parts, "De die judicii" and " Lacrimosa ".

Lux Aeterna (1966) is a 16-voice a cappella piece whose text is also associated with the Latin Requiem.

Ligeti's Cello Concerto (1966), which is dedicated to Siegfried Palm, is composed of two movements: the first begins with an almost imperceptible cello which slowly shifts into static tone clusters with the orchestra before reaching a crescendo and slowly decaying, while the second is a virtuoso piece of dynamic atonal melody on the part of the cello.

Lontano (1967), for full orchestra, is another example of micropolyphony, but the overall effect is closer to harmony, with complex woven textures and opacity of the sound giving rise to a harmonious effect. It has become a standard repertoire piece.

String Quartet No. 2 (1968) consists of five movements. They differ widely from each other in their types of motion. In the first, the structure is largely broken up, as in Aventures. In the second, everything is reduced to very slow motion, and the music seems to be coming from a distance, with great lyricism. The pizzicato third movement is a machine-like studies, hard and mechanical, whereby the parts playing repeated notes create a "granulated" continuum. In the fourth, which is fast and threatening, everything that happened before is crammed together. Lastly, in strong contrast, the fifth movement spreads itself out. In each movement, the same basic configurations return, but each time their colouring or viewpoint is different, so that the overall form only really emerges when one listens to all five movements in context.

Ramifications (1968–69), completed a year before the Chamber Concerto, is scored for an ensemble of strings in twelve parts—seven violins, two violas, two cellos and a double bass—each of which may be taken by one player or several. The twelve are divided into two numerically equal groups but with the instruments in the first group tuned approximately a quarter-tone higher (four violins, a viola and a cello). As the group play, the one tuned higher inevitably tends to slide down toward the other, and both get nearer each other in pitch.

In the Chamber Concerto (1969–70), several layers, processes and kinds of movement can take place on different planes simultaneously. In spite of frequent markings of "senza tempo", the instrumentalists are not given linear freedom; Ligeti insists on keeping his texture under strict control at any given moment. The form is like a "precision mechanism". Ligeti was always fascinated by machines that do not work properly and by the world of technology and automation. The use of periodic mechanical noises, suggesting not-quite-reliable machinery, occurs in many of his works. The scoring is for flute (doubling piccolo), oboe (doubling oboe d'amore and cor anglais), clarinet, bass clarinet (doubling second clarinet), horn, trombone, harpsichord (doubling Hammond organ), piano (doubling celesta), and solo string quintet. He also wrote a Double Concerto for Flute, Oboe & Orchestra (1972).

Most of these compositions establish timbre, rather than the traditionally-favored dimensions of pitch and rhythm, as their principal formal parameter, a practice that has come to be known as sonorism. From the 1970s, Ligeti turned away from sonorism and began to concentrate on rhythm. Pieces such as Continuum (1968) and Clocks and Clouds (1972–73) were written before he heard the music of Steve Reich and Terry Riley in 1972. But the second of his Three Pieces for Two Pianos (1976), entitled "Self-portrait with Reich and Riley (and Chopin in the background)", commemorates this affirmation and influence. During the 1970s, he also became interested in the polyphonic pipe music of the Banda -Linda tribe from the Central African Republic, which he heard through the recordings of one of his students.

In 1977, Ligeti completed his only opera, Le Grand Macabre, thirteen years after its initial commission. Loosely based on Michel de Ghelderode 's 1934 play, La balade du grand macabre, it is a work of Absurd theatre —Ligeti called it an "anti-anti-opera"—in which Death (Nekrotzar) arrives in the fictional city of Breughelland and announces that the end of the world will occur at midnight. Musically, Le Grand Macabre draws on techniques not associated with Ligeti's previous work, including quotations and pseudo-quotations of other works and the use of consonant thirds and sixths. After Le Grand Macabre, Ligeti would abandon the use of pastiche, but would increasingly incorporate consonant harmonies (even major and minor triads) into his work, albeit not in a diatonic context.
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