Speaking historically, there are two main approaches to composing electronically. One approach is to manipulate recorded sounds – natural sounds, or simply any sound recorded on tape. This approach is called Concrete Music (musique concrete) because the composer is manipulating actual sound, rather than notation (an abstraction, or representation of sound). The other approach involves using electronic equipment to generate waveforms that produce sound. This approach is called synthesis.
With the development of computer technology, concrete music is enjoying renewed interest. Computers also make it easier to analyze a sound to discover its component parts and manipulate them individually. Synthesizers allow the composer to exert more control over sound and its spectra. Post WWII serialists tended to favor synthesis for the control it offered.