diff --git a/src/processors/BaseProcessor.h b/src/processors/BaseProcessor.h
index 0ce6869e..d0c576c5 100644
--- a/src/processors/BaseProcessor.h
+++ b/src/processors/BaseProcessor.h
@@ -159,7 +159,8 @@ class BaseProcessor : private JuceProcWrapper
     /** Returns the netlist circuit quantities, or nullptr if the processor has no circuit quantities. */
     auto* getNetlistCircuitQuantities() { return netlistCircuitQuantities.get(); }
 
-    AudioBuffer<float>& getInputBuffer (int idx = 0) { return inputBuffers.getReference (idx); }
+    const AudioBuffer<float>& getInputBuffer (int idx = 0) const { return inputBuffers.getReference (idx); }
+    AudioBuffer<float>& getInputBufferNonConst (int idx = 0) { return inputBuffers.getReference (idx); } // Most derived classes should never use this!
     AudioBuffer<float>* getOutputBuffer (int idx = 0) { return outputBuffers[idx]; }
     const ConnectionInfo& getOutputConnection (int portIdx, int connectionIdx) const { return outputConnections[portIdx].getReference (connectionIdx); }
 
diff --git a/src/processors/chain/ProcessorChain.cpp b/src/processors/chain/ProcessorChain.cpp
index 4fc1c07c..94da0456 100644
--- a/src/processors/chain/ProcessorChain.cpp
+++ b/src/processors/chain/ProcessorChain.cpp
@@ -134,13 +134,13 @@ void ProcessorChain::runProcessor (BaseProcessor* proc, AudioBuffer<float>& buff
         }
         else if (nextNumProcs > 1 && nextNumInputs == 1)
         {
-            auto& copyNextBuffer = nextProc->getInputBuffer();
+            auto& copyNextBuffer = nextProc->getInputBufferNonConst();
             copyNextBuffer.makeCopyOf (nextBuffer, true);
             runProcessor (nextProc, copyNextBuffer, outProcessed);
         }
         else
         {
-            auto& copyNextBuffer = nextProc->getInputBuffer (inputIndex);
+            auto& copyNextBuffer = nextProc->getInputBufferNonConst (inputIndex);
             copyNextBuffer.makeCopyOf (nextBuffer, true);
 
             nextProc->incrementNumInputsReady();
diff --git a/src/processors/utility/Mixer.cpp b/src/processors/utility/Mixer.cpp
index 98b6cada..3c57eaf7 100644
--- a/src/processors/utility/Mixer.cpp
+++ b/src/processors/utility/Mixer.cpp
@@ -54,7 +54,7 @@ void Mixer::processAudio (AudioBuffer<float>& buffer)
 
         numInputsProcessed++;
 
-        auto& inBuffer = getInputBuffer (i);
+        auto& inBuffer = getInputBufferNonConst (i);
         int numChannels = inBuffer.getNumChannels();
         int numSamples = inBuffer.getNumSamples();
 
@@ -108,7 +108,7 @@ void Mixer::processAudioBypassed (AudioBuffer<float>& buffer)
     {
         if (inputsConnected.contains (i))
         {
-            auto& inBuffer = getInputBuffer (i);
+            auto& inBuffer = getInputBufferNonConst (i);
             outputBuffers.getReference (0) = &inBuffer;
             return;
         }
diff --git a/src/processors/utility/StereoMerger.cpp b/src/processors/utility/StereoMerger.cpp
index bf340947..ee98f8b6 100644
--- a/src/processors/utility/StereoMerger.cpp
+++ b/src/processors/utility/StereoMerger.cpp
@@ -68,7 +68,7 @@ void StereoMerger::processAudio (AudioBuffer<float>& buffer)
 
     if (isInput0Connected)
     {
-        auto& inBuffer = getInputBuffer (LeftChannel);
+        auto& inBuffer = getInputBufferNonConst (LeftChannel);
         makeBufferMono (inBuffer);
 
         stereoBuffer.addFrom (0, 0, inBuffer, 0, 0, numSamples);
@@ -78,7 +78,7 @@ void StereoMerger::processAudio (AudioBuffer<float>& buffer)
 
     if (isInput1Connected)
     {
-        auto& inBuffer = getInputBuffer (RightChannel);
+        auto& inBuffer = getInputBufferNonConst (RightChannel);
         makeBufferMono (inBuffer);
 
         if (isLeftRight)