diff --git a/plugin/module.cpp b/plugin/module.cpp
index 72a2066..bcad0f4 100644
--- a/plugin/module.cpp
+++ b/plugin/module.cpp
@@ -25,24 +25,24 @@ Module::Module() {
 
 void Module::run(Voice* voice) {
     // run updates for module board
+
+    // work out the "master" cutoff
+    vcfCutoff = patchRam.vcfFreq / 127.0f;
+    vcfCutoff += lfo * (patchRam.vcfLfo/127.0f);
+
     for (uint32_t i = 0; i < NUM_VOICES; i++) {
         switch (voice[i].envPhase) {
-            case 0:
-                voice[i].envTarget = 0;
-                voice[i].envTc = 1-(decayTable[patchRam.env_r] / 65536.0f);
-        voice[i].env = (voice[i].envTarget - voice[i].env) * voice[i].envTc + voice[i].env;
+            case 0:                                                     // release phase FIXME use an enum I guess
+                voice[i].env *= decayTable[patchRam.env_r] / 65536.0f;  // "RC" decay to zero
                 break;
-            case 1:
-                voice[i].envTarget = 1;
-                voice[i].env += attackTable[patchRam.env_a] / 65536.0f;
+            case 1:                                                      // attack phase
+                voice[i].env += attackTable[patchRam.env_a] / 65536.0f;  // linear attack to 1
                 break;
             case 2:
-                voice[i].envTarget = patchRam.env_s / 127.0f;
-                voice[i].envTc = 1 - (decayTable[patchRam.env_d] / 65536.0f);
-                voice[i].env = (voice[i].envTarget - voice[i].env) * voice[i].envTc + voice[i].env;
+                float t = patchRam.env_s / 127.0f;
+                voice[i].env = (voice[i].env - t) * (decayTable[patchRam.env_d] / 65536.0f) + t;
                 break;
         }
-        //voice[i].env = (voice[i].envTarget - voice[i].env) * voice[i].envTc + voice[i].env;
         if (voice[i].env > 1.0f) {
             voice[i].env = 1.0f;
             voice[i].envPhase = 2;  // flip to decay
diff --git a/plugin/module.hpp b/plugin/module.hpp
index 6ba1b3c..22d4492 100644
--- a/plugin/module.hpp
+++ b/plugin/module.hpp
@@ -32,6 +32,7 @@ class Module {
     void run(Voice* voice);
     // Voice voices[NUM_VOICES];
     float vcfCutoff = 0, vcfReso = 0;
+    float lfo = 0, lfoTheta = 0;
 
     // precomputed values for all voices
     float pw, saw, square, sub;
@@ -65,10 +66,7 @@ class Voice {
     void off();
     void run(Module* m, float* buffer, uint32_t samples);
     uint8_t envPhase = 0;
-    float env = 0;                // output amplitude
-    float envTc = 0;
-    float envTarget = 0;
-
+    float env = 0;  // output amplitude
 
    private:
     float omega = 0, theta = 0;   // phase increment and angle
@@ -77,8 +75,7 @@ class Voice {
     float subosc = 1;             // sub oscillator flipflop output
 
     // filter
-    float b1=0, b2=0, b3=0, b4=0;
+    float b1 = 0, b2 = 0, b3 = 0, b4 = 0;
 };
 
-
 #endif
\ No newline at end of file