Stephen A. Taylor, Chopin, Pygmies, and Tempo Fugue: Ligeti's "Automne a Varsovie", Vol 3.3., Online Journal of the Society for Music Theory.
I looked up 'shimmering' on ODO. David Bruce explains this at 2:22, but I still don't understand.
[1.2] He produces these polyrhythms by combining two vastly different sources of inspiration: the Romantic-era piano music of Chopin and Schumann, and the indigenous music of sub-Saharan Africa. The composer writes:
One often arrives at something qualitatively new by unifying two already known but separate domains. In this case, I have combined two distinct musical ideas: the hemiola of Schumann and Chopin, which depends on meter, and the additive pulsation principle of African music. . . [T]he hemiola arises from the metric ambiguity posed by a measure of six beats, which can either be divided in three groups of two or in two groups of three. . . The shimmering effect of dividing the bar simultaneously into two and three produces the metric tension which is one of the most seductive attractions of the music of Chopin, Schumann, Brahms, and Liszt.
A completely different metric ambiguity occurs in African music. Here there are no measures in the European sense, but instead two rhythmic levels: a ground layer of fast, even pulsations which are not counted as such but rather felt, and a superimposed, upper layer of occasionally symmetrical, but more often asymmetrical, patterns of varying length.{1}
- Gyorgy Ligeti, "On My Etudes for Piano," trans. Sid McLauchlan, Sonus 9/1 (1988): 4-5. An abbreviated version appears in the liner notes to Erato Compact Disc ECD 75555.
