diff --git a/Source/FXProcessor.cpp b/Source/FXProcessor.cpp
index 72a296b..3e4e9a8 100644
--- a/Source/FXProcessor.cpp
+++ b/Source/FXProcessor.cpp
@@ -14,24 +14,27 @@ namespace serum
 
 FXProcessor::FXProcessor()
 {
-    units[0] = std::make_unique<HyperUnit>();
-    units[1] = std::make_unique<ChorusUnit>();
-    units[2] = std::make_unique<FlangerUnit>();
-    units[3] = std::make_unique<PhaserUnit>();
-    units[4] = std::make_unique<DistortionUnit>();
-    units[5] = std::make_unique<EQUnit>();
-    units[6] = std::make_unique<CompressorUnit>();
-    units[7] = std::make_unique<DelayUnit>();
-    units[8] = std::make_unique<ReverbUnit>();
+    for (auto& slotUnits : units)
+    {
+        slotUnits[0] = std::make_unique<HyperUnit>();
+        slotUnits[1] = std::make_unique<ChorusUnit>();
+        slotUnits[2] = std::make_unique<FlangerUnit>();
+        slotUnits[3] = std::make_unique<PhaserUnit>();
+        slotUnits[4] = std::make_unique<DistortionUnit>();
+        slotUnits[5] = std::make_unique<EQUnit>();
+        slotUnits[6] = std::make_unique<CompressorUnit>();
+        slotUnits[7] = std::make_unique<DelayUnit>();
+        slotUnits[8] = std::make_unique<ReverbUnit>();
+    }
 }
 
 FXProcessor::~FXProcessor() = default;
 
 void FXProcessor::prepare (double sampleRate, int maxBlockSize)
 {
-    for (auto& u : units)
-        u->prepare (sampleRate, maxBlockSize);
-    dry.setSize (2, maxBlockSize, false, false, true);
+    for (auto& slotUnits : units)
+        for (auto& u : slotUnits)
+            u->prepare (sampleRate, maxBlockSize);
     wet.setSize (2, maxBlockSize, false, false, true);
     reset();
 }
diff --git a/Source/FXProcessor.h b/Source/FXProcessor.h
index 9eb6876..bc3919a 100644
--- a/Source/FXProcessor.h
+++ b/Source/FXProcessor.h
@@ -31,7 +31,7 @@ struct FxSlotParams
 // ===========================================================================
 // Reorderable effects rack. Slots are processed in list order; reordering is
 // simply swapping FxSlotParams entries. Nine effect unit implementations are
-// owned here and shared across slots.
+// preconstructed per slot with independent DSP history.
 // ===========================================================================
 class FXProcessor
 {
@@ -47,8 +47,10 @@ public:
     static juce::String fxTypeName (int type);
 
 private:
-    std::array<std::unique_ptr<FXUnit>, 9> units;
-    juce::AudioBuffer<float> dry, wet;
+    static constexpr int kNumEffectTypes = (int) FxType::Count - 1;
+    std::array<std::array<std::unique_ptr<FXUnit>, kNumEffectTypes>, kNumFxSlots> units;
+    std::array<int, kNumFxSlots> activeTypes {};
+    juce::AudioBuffer<float> wet;
 };
 
 } // namespace serum