What is the theme in Hum by Ann Lauterbach?

The passage of time is a major theme in these poems. Lauterbach's repetition of the words “yesterday,” “today,” and “tomorrow” make the passage of time a major theme in “Hum.” The puzzlelike framework in which the terms are placed underscores the sense of dislocation the narrator must be feeling. At various points, she states, “Tomorrow was yesterday” and “The towers are yesterday.” The first statement implies that the day before had been a fateful “tomorrow”—a day whose events had been long in coming. Yesterday, also, the towers existed. Yesterday things were different and perhaps more hopeful.