Most of the extended instrumental playing techniques, as well as electroacoustic music in general, are still deprived of a conventional method of notation. In order to facilitate the utilisation of these unconventional musical elements, a coherent and consistent notation system is developed in this work. Numerous extended techniques for playing string instruments, wind instruments, percussion instruments, keyboard instruments and vocal techniques, as well as the essential components of sound synthesis, audio processing and sound recording, are therefore systematically explained and previous methods of notation discussed.