Ligeti, Lux Aeterna
Lux Aeterna is a choral piece for 16 voices. The whole sections are composed as canons. The canons are, however, not perceptible. Ligeti has coined the term ‘micropolyphony’, and it refers to the compositional process in which "polyphony is written, but harmony is heard. […] The polyphonic structure does not come through, you cannot hear it; it remains hidden in a microscopic, underwater world, to us inaudible. I call it micropolyphony (such a beautiful word)”. (Ligeti). Word ‘harmony’ should be understood here as sonority, rather than chords. Because, very often we hear chromatic and diatonic clusters, and other pitch-assemblages of very diverse interval-structure. The ‘sound-mass’ is constantly being transformed, and this is perceived as one of the ‘stories’ of Lux Aeterna. The texture is one of the most important parameters here.
The theme is melodic, but its melody is not perceptible. This is the result of several factors: 1) the themes that are imitated in canons are rhythmically not clearly profiled (and the notes are quite long), and even more important, its imitations all have different rhythm (the pitch progression is the only canonic element), 2) the themes are imitated in very close stretti, in the unison, and with almost inaudible beginning (composers directives), 3) the piece is vocal, which means that timbres can easily blend, 4) most parts of all the themes are progressing in stepwise motion, also often returning to a previous position. The combination of these conditions blur the horizontal dimension. Voices in the same register blend, and the listener cannot discern which of them has moved to the next audible pitch.
Lux Aeterna opens on one pitch, F, and due to its long duration and repetitions, eight voices will sing it in unison before the second note of the canon (E) sounds. The image below shows the first bars. The soprano 1 part exposes the first five notes of the theme (F-F-F-E-F-). The blue lines show the moments any new F tone sounds: except from the very beginning, none of them starts simultaneously. Soft entrances just slightly change the timbre of the united F tone. Purple lines show the moments any new E sounds. These tones also merge into one E, with variable texture (timbre). Each pitch is felt as one tone, but this one tone is very dynamic, softly trembling as the new singers join it, thinning out as they, one by one, leave it.
The following image shows the duration of each tone; blue lines represent pitch F, purple lines represent pitch E. The emergence of new pitch E happens under the still sounding pitch F. Now they sound together, as two layers, next to each other. The return of F at the end of m.4 is not perceived as a new tone in the horizontal sequence but rather as thickening of the F that still sounds in other voices. Each new pitch (that does not already sound) becomes a new layer, for as long as it sounds.
The pitch collection gradually grows, adding new pitches as new layers. The texture becomes thicker, denser.
In the image above we can see that the opening pitch F is present for a long time (it is the first, the third, the seventh pitch in the theme). Also some other pitches that are recurring in the sequence are present for a very long time. Although these pitches are realized by many shorter entrances, there is always at least one voice that sings a particular pitch at any moment. In this way, all of them blend in long tones. The following graph shows continuous pitch presence in the first 8 bars:
The graphic representations used in the current text (and possibly also in the linked video) are inspired by the analysis published by Jonathan W. Bernard (1994).
The unfolding of Lux Aeterna is characterized by the transformation of the tone collection on time-axes. Moments such as the one when tone collection suddenly becomes diatonic are memorable (e.g. the full Db-major scale in m.13). The embedded video translates the pitches into colors, showing the change of the palette, as the sound mass changes its properties. Although the melody of the canon (the horizontal dimension of each part/voice) is not perceived, Lux Aeterna certainly does have a melodic line. It is created from the new pitches that appear outside of any current cluster. The ‘opening melody’ so becomes F-E-G-Eb-Ab. It represents the widening of the texture, the growing of the sound mass.
Lux Aeterna does not feature pedals nor drones that are visible in the score. Interaction of the rhythmic-, melodic-, imitational organization, articulation, and timbre of the voices results in the illusion that the piece is made from sound layers. Each layer is defined by its pitch, while its timbre is variable. In this way each (compound) layer contributes in any particular moment to the ‘harmony’ of the piece, while the transformations in its timbre influence the total sound. The unfolding of Lux Aeterna could be perceived as a process of transformation of the sound mass (with a number of musical events related to pitch), and its constituting parts could be perceived as textural drones. Even if it is an illusion.
 György Ligeti in conversation with Péter Várnai, Josef Häusler, Claude Samuel, and himself (Eulenburg, 1983)