This document discusses new musical styles that emerged in the 20th century, including electronic music, musique concrete, and chance music. It provides details on influential composers like Edgar Varese, Karlheinz Stockhausen, and John Cage who pioneered these new styles. Electronic music uses tape recorders and other technology to manipulate sounds. Chance music, also called aleatoric music, involves incorporating random external sounds and leaving elements of a musical performance to chance. The document includes a Venn diagram activity comparing electronic music and chance music, and process questions about their similarities and differences. Students are assigned to bring materials that can produce sounds for a performance activity in the next meeting.