From fcadaf3980a2160f85f87b6d86300d2b77cf058d Mon Sep 17 00:00:00 2001
From: Gordon JC Pearce <gordonjcp@gmail.com>
Date: Mon, 18 Aug 2025 00:27:23 +0100
Subject: [PATCH] pretty reasonable viola

---
 plugin/generator.cpp | 35 ++++++++++++++++++++++++++++-------
 plugin/generator.hpp |  3 +++
 2 files changed, 31 insertions(+), 7 deletions(-)

diff --git a/plugin/generator.cpp b/plugin/generator.cpp
index 24c0108..2d9a03a 100644
--- a/plugin/generator.cpp
+++ b/plugin/generator.cpp
@@ -53,34 +53,55 @@ void Generator::runBlock(float *output, uint8_t *noteTable, uint32_t frames) {
         for (k = 0; k < NUM_VOICES; k++) {
             key = noteTable[k] & 0x7f;
             n1 = key % 12, n2 = (key / 12 - 3);
+            v = &voices[k];
+
             d = (phase[n1] & (0x40000000 >> n2)) != 0;
             n = d ? 0.25 : -0.25;
-
-            v = &voices[k];
             v->vc34 = ((n - v->vc34) * v->c34) + v->vc34;
             n -= v->vc34;
             n *= d ? 1 : 0;
-
             v->vc78 = ((n - v->vc78) * v->c78) + v->vc78;
             v->vc107 = ((v->vc78 - v->vc107) * v->c107) + v->vc107;
 
+
+
+            d = (phase[n1] & (0x80000000 >> n2)) != 0;
+            n = d ? 0.25 : -0.25;
+            v->vc33 = ((n - v->vc33) * v->c33) + v->vc33;
+            n -= v->vc33;
+            n *= d ? 1 : 0;
+            v->vc22 = ((n - v->vc22) * v->c22) + v->vc22;
+            v->vc31 = ((v->vc31 - v->vc31) * v->c31) + v->vc31;
+
+
             v->vca = ((v->gate - v->vca) * v->vcatc) + v->vca;
 
-            output[i] += (v->vc78 - v->vc107) * v->vca;  //((noteTable[k]&0x80)?0:1);
+            float v4 = (v->vc78 - v->vc107);
+            float v8 = (v->vc22 - v->vc31);
+
+            output[i] += (v4 + v8) * v->vca;  //((noteTable[k]&0x80)?0:1);
         }
     }
 }
 
 void Voice::startNote(uint8_t key, double sampleRate) {
     // start a new note
-    // float fc = 88.4 * powf(2, 0.083334 * (key - 36));
-    // c34 = powf((1 - 2 * fc / sampleRate), 2);
+    // violin and viola filter params
     float fc = 88.4 * powf(2, 0.083334 * (key - 24));
     c34 = 1 - exp(-6.283 * fc / 48000.0);
+    c33 = 1 - exp(-6.283 * fc /2 / 48000.0);
+
+    // violin register
     fc = 4000 * powf(2, 0.06 * (key - 24));
     c78 = 1 - exp(-6.283 * fc / 48000.0);
     c107 = 1 - exp(-6.283 * 154.0 / 48000.0);
-    // printf("key = %d, shaper cutoff = %f, coefficient = %f %f\n", key, fc, c78, c34);
+
+    // viola register
+    fc = 6000 * powf(2, 0.07 * (key - 24));
+    c22 = 1 - exp(-6.283 * fc / 48000.0);
+    c31 = 1 - exp(-6.283 * 54.0 / 48000.0);
+
+
     gate = 1;
     vcatc = 0.0001;
 }
diff --git a/plugin/generator.hpp b/plugin/generator.hpp
index a222842..0b36a75 100644
--- a/plugin/generator.hpp
+++ b/plugin/generator.hpp
@@ -34,7 +34,10 @@ class Voice {
 
    private:
     uint8_t semi, oct;
+    float c22 = 0, vc22 = 0;
+    float c31 = 0, vc31 = 0;
     float c34 = 0, vc34 = 0;
+    float c33 = 0, vc33 = 0;
     float c78 = 0, vc78 = 0;
     float c107 = 0, vc107 = 0;
     float vca = 0, vcatc = 0, gate = 0;