First appearing in the 1950's, by the end of the 1960's Synthesizers were appearing on many mainstream records. The Beatles, The Beach Boys and The Who were just a few of the artists to experiment with this new sound. From then on, Synths have defined themselves as a musical instrument in their own right. Analogue Synths use circuitry and often Valves to create tones, where newer PCM and Physical Modelling synthesizers utilise digital recordings and software tone generators to create sound.