The piece is not descriptive of the aftershocks experienced following earthquakes, although the choice of title was prompted by earthquakes, and people’s reaction to the aftershocks, in El Salvador in the early part of 2001. Rather it refers to the nervous reaction suffered by people who have faced extremely stressful or shocking events, and their tendency to over-react to less serious events of the same kind, as if the horror had returned.
The piece has four flexibly instrumented lines, each of which could be played on several different instruments. Each lines requires some instruments capably of sustaining a quiet drone for some bars. There is also a percussion part requiring several drums and a cymbal.