Tutorials and Topics - Peabody Computer Music

Tutorial 9Synthesis:Amplitude modulationThe two MSP patches that made these examples are shown below.Ring modulationAmplitude modulationThe difference in effect is due to the constant value of 0.75 in the AM patch, which isvaried by a modulator of lesser amplitude. This constant value can be thought of as thecarrier’s amplitude, which is varied by the instantaneous amplitude of the modulator. Theamplitude still varies according to the shape of the modulator, but the modulator is notcentered on 0.Technical detail: The amount that a wave is offset from 0 is called the DCoffset. A constant amplitude value such as this represents spectral energyat the frequency 0 Hz. The modulator in AM has a DC offset, whichdistinguishes it from ring modulation.109