Additive Synthesis, Tremolo, Ring Modulation

Additive synthesis is simply combining two or more signals into a single waveform. When two waves are added together, the new waveform contains characteristics of all the signals combined to make it. Amplitude modulation synthesis is where the gain of one signal is modulated by the gain of another signal. Tremolo is a form of AMS where the gain of an audio signal is changed at a slow rate often at a frequency below the range of hearing (20 Hz). It is often used as an effect for organs or electric guitar. Ring modulation is where one audio signal is modulated with another audio signal, which has both positive and negative values. It is often used to create alien voices or distort an analog signal with a digital one.