Extended techniques refer to unconventional methods of producing sound on musical instruments, expanding their expressive capabilities beyond traditional playing. These techniques can include multiphonics, where a musician produces multiple notes simultaneously, or using unconventional materials to create unique timbres. These methods are often employed in contemporary classical music, jazz, and experimental genres. Composers like John Cage and George Crumb have popularized extended techniques, encouraging musicians to explore new sonic possibilities. By incorporating these techniques, performers can create innovative soundscapes that challenge the listener's perception of music.