"Aleatory music" is music in which some element of the composition is left to chance, and/or some primary element of a composed work's realization is left to the determination of its performer(s). The term became known to European composers through lectures by acoustician Werner Meyer-Eppler at the Darmstadt International Summer Courses for New Music in the beginning of the 1950s. According to his definition, "a process is said to be aleatoric ... if its course is determined in general but depends on chance in detail".
An empanada, the food Juan making for Hermann and Weltraud, is a type of baked or fried turnover consisting of pastry and filling, common in Southern European, Latin American, and the Philippines cultures. As mentioned by Juan, in Chile, empanadas are a staple part of the national cuisine. Commonly consumed in large quantities during the country's national day celebrations, many Chileans consider this to be their most representative dish. The most common type of Chilean empanada is what is referred to as the empanada de pino, it is a baked empanada filled with diced or ground beef sautéed with onions and spices, half of a hard boiled egg, an olive and raisins (although the latter is not liked by a sizable portion of the population).
The episode takes place on 22 November 1963, the day JFK was assassinated.
The several quotes from Wittgenstein by Alex is from "Tractatus Logico-Philosophicus".
"Spuren", the title of Herman's planned concert, means "Traces".