
"Shown is an edit screen from the JD-990. This is the "structure" page, which determines how the processing blocks are to be organized in a given patch. The ability to do this is one of the improvements that the JD-990 has over the JD-800; the JD-800's processing architecture is fixed in the configuration shown on the left side. On the right side, we see a ring-modulation type patch. Tone C goes through a TVA (equivalent to a VCA), and then is multiplied by tone D. (The "R" in the box represents ring modulation, which is implemented in the digital realm by simple multiplication of the individual samples from each input. Ring modulation is one of the few synth functions that is difficult to do well in analog circuitry, but trivially easy to do in digital synthesis.) The patch then passes through two TVFs (equivalent to VCFs), and a final TVA to shape the output."
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