JP8000 SuperSaw Algorithm

Courtesy to The Usual Suspects’ reverse engineering work, documented in https://www.youtube.com/watch?v=XM_q5T7wTpQ&t=1601s

• It’s 7 naive saw waves, passed through an highpass filter
• Trick: the JP8000 is running at 88.2KHz !
• No modulation, no phase tricks, no chorus, no magic.

  int24_t saw[7] = {0};
  const int24_t detune_table[7] = { 0, 128, -128, 816, -824, 1408, -1440 };
  int24_t next(int24_t pitch, int24_t spread, int24_t detune) {
   int24_t sum = 0;
   for (int i = 0; i < 7; i++) {
   int24_t voice_detune = (detune_table[i] * (pitch * detune)) >> 7;
   saw[i] += pitch + voice_detune;
   if (i == 0)
   sum += saw[i];
   else
   sum += saw[i] * spread;
   }
   return high_pass(sum);
  }