Sentence:  Called “James Tenney and Milton Babbitt : American Iconoclasts,” the mini-festival begins on Saturday with a work by Mr. Tenney, who died in 2006, on a program including pieces by Larry Polansky, Michael Byron and Henry Cowell (the 1925 “Ensemble” for string quartet and <WSD>thundersticks</WSD>). Mr. Babbitt is honored on Sunday with a program that includes, among other works, a premiere by Christopher Buchenholz. 
Meaning of the word marked with <WSD> tags:  A narrow plastic balloon that is used as a promotional noise maker by hitting one against another.