Ligeti’s Lux aeterna is written for sixteen solo singers and chorus; often they sing chords that include all twelve pitches of the chromatic scale. We need a new vocabulary even to talk about music such as this, and some new diagrams — our pitch-time graph on page 24, which indicated melodies by lines, doesn’t work for Ligeti’s sound complexes. To represent them and show how they develop over time, we can use nonmusical figures:

Lux aeterna starts with a single pitch, which Ligeti “expands” both upward and downward by slowly adding a dense mix of pitches above and below it. At other times he starts with a single pitch and expands it upward (adding mainly higher pitches) or downward (adding lower ones). Starting with a full-range sound, Ligeti can “contract” it: either downward (by removing notes till only a single low pitch remains), or upward, or to some pitch in the middle — an effect that can be called “focusing,” by analogy to a camera lens.

Once we have accustomed our ears to the astonishing rich sonorities that are revealed by the slow ebbing and flowing of Ligeti’s sound complexes, we can appreciate that the musical form of Lux aeterna is simplicity itself. Four slow sound surges make up the piece (see the separate tracks in Listening Chart 27). The first, for women, expands out to a big sound complex and then fouses upward to a high single pitch in octaves. It is balanced by the second surge, for men, and the fourth, for men and women, both of which expand and then focus downward. In between comes the climax of the piece, the explosion of men’s and women’s voices that begins the third surge.

The words of Lux aeterna are taken from the Requiem Mass, but they can scarcely be heard and understood; the piece is a study in sheer vocal sonority. Ligeti wrote other sound-complex pieces employing other forces, such as Atmosphères for full orchestra. Lux aeterna is his most famous work, thanks to its use in the 1968 Stanley Kubrick film classic 2001: A Space Odyssey.