From the course: Learning Modular Synthesis

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Ring modulation (AM)

Ring modulation (AM)

- Now let's play with amplitude modulation. Again, you say, "Hey, a few movies ago "we did tremolo, we did an LFO changing the loudness "of an oscillator." But when that second oscillator is up at audio rates, very strange things happen. When one oscillator is changing the loudness of another oscillator, at audio frequencies, they add together their frequencies and subtract them from each other. So if you had, say, a harmonic of 100 hertz and another harmonic at 200 hertz, the result would be one plus two, 300, and two minus one, 100 hertz. One and three, totally different harmonic spectrum. If they aren't tuned at nice intervals, you get strange metallic harmonics. Now, you may try to do this with a normal VCA but you'll run into some issues. One, your normal voltage-controlled amplifier may not be able to change loudness fast enough to keep up with an audio-rate oscillator. Two, most voltage-controlled amplifiers don't go below zero. You hit zero volts, they stop right there, they…

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