PIPELINE - TREMOLO / HARMONIC VIBRATO

Amplitude modulation, otherwise known as tremolo, is arguably the first 'overt' guitar effect. Amplifiers with built-in tremolo began appearing by the late 40's, and became standard equipment by the late 50's. The first major style of music to adopt tremolo as it's own was surf music - groups like the Del-Tones, the Ventures and the Chantays combined tremolo with reverb to create the definitive surf guitar sound.