THE ELECTRONIC WORKS OF GYÖRGY LIGETI AND THEIR ...

produced as one continuous glissando, interrupted by additional filtering. This creates the
impression of one glissando fading out and back in, rather than one glissando ending and a
second beginning. 9
The entrance of Event 2 at 12" marks the first downward glissando, an event
which creates an axis of symmetry around 13.3", and which begins an acceleration in the
accumulation of density. While the material is the same–20 Hz noise grouped into similar
numbers of bands–and the pacing is initially in units of 3 seconds, with entrances at 12, 15,
and 18 seconds, Event 2 begins to accelerate from the precedent set by Event 1. After the
3 second interval separating the first 3 entrances, the fourth group begins at 20", after only
2 seconds, and subsequent entrances gain speed steadily.
Although the second event’s material consists of the same bands of 20 Hz noise as
in the first event, Ligeti substantially increases the overall density, aligning not merely the
continuations of various strands, but also the peaks and troughs of the ascending and
descending glissandi to fill out more of the spectrum at once. This alignment results in the
characteristic cross-hatching pattern seen in the spectrograph above (Figure 2.3). The axis
of symmetry at 13.3" is one clear example of this, which will be invariant when
retrograded, and will sound the same when it occurs in that form towards the end of the
piece; moreover, the steadily increasing density of the cross-hatching pattern through the
9
This technique, while more crudely constructed, resembles Shepards Tones (described by Roger N.
Shepard “Circularity in Judgements of Relative Pitch” Journal of the Acoustical Society of America, vol.
36 no. 12 (1964), 2346-2353) in which tones are carefully arranged to produce the illusion of a
continually rising (or falling) sound.
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