Our listening example by Ligeti features a compositional technique the he developed called micropolyphony. You’ll find a number of musical terms referenced in this article. Two that I particularly want you to understand are canon and cluster chord. Canon is a strict form of imitative polyphony (linear or horizontal), while a cluster chord is a harmonic structure (vertical).
Once again, we’re seeing the importance of texture in the compositional process. What’s interesting here is that Ligeti is using a polyphonic texture (lots of little imitated lines) to create a sound that is very similar to a tightly-clustered chord or stack of pitches. You might ask, why not simply write a cluster chord? You’ll hear some cluster chords or tone clusters later in the music of Arvo Part. I believe Ligeti would say that the constant movement of the lines in his micropolyphony creates a dynamic quality where a cluster chord seems more static. I encourage you to compare the dissonant structures of the two composers to see if you agree that there is a difference.
Micropolyphony is a kind of polyphonic musical texture developed by György Ligeti and then imitated by some other twentieth-century composers, which consists of many lines of dense canons moving at different tempos or rhythms, thus resulting in tone clusters vertically. According to David Cope, “micropolyphony resembles cluster chords, but differs in its use of moving rather than static lines”; it is “a simultaneity of different lines, rhythms, and timbres.”
Differences between micropolyphonic texture and conventional polyphonic texture can be explained by Ligeti’s own description:
Technically speaking I have always approached musical texture through part-writing. Both Atmosphères and Lontano have a dense canonic structure. But you cannot actually hear the polyphony, the canon. You hear a kind of impenetrable texture, something like a very densely woven cobweb. I have retained melodic lines in the process of composition, they are governed by rules as strict as Palestrina’s or those of the Flemish school, but the rules of this polyphony are worked out by me. 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!).
The earliest example of micropolyphony in Ligeti’s work occurs in the second movement (mm 25–37) of his orchestral composition Apparitions (Steinitz 2003, 103). His next work,Atmosphères for orchestra, the first movement of his later Requiem, for soprano, mezzo-soprano, mixed choir, and orchestra, the uncompanied choral work Lux aeterna, and Lontanofor orchestra, also use the technique. Micropolyphony is easier with larger ensembles or polyphonic instruments such as the piano, though the Poème symphonique for a hundred metronomes creates “micropolyphony of unparallelled complexity.” Many of Ligeti’s piano pieces are examples of micropolyphony applied to complex “minimalist” Steve Reich and Pygmy music derived rhythmic schemes.