diff --git a/src/finer/PhaseAdvance.h b/src/finer/PhaseAdvance.h
index f5a6496..1c1384f 100644
--- a/src/finer/PhaseAdvance.h
+++ b/src/finer/PhaseAdvance.h
@@ -94,6 +94,7 @@ public:
                  const process_t *const *prevMag,
                  const Guide::Configuration &configuration,
                  const Guide::Guidance *const *guidance,
+                 bool usingMidSide,
                  int inhop,
                  int outhop) {
 
@@ -197,6 +198,9 @@ public:
                 process_t ph = 0.0;
                 if (inRange(f, g->phaseReset) || inRange(f, g->kick)) {
                     ph = phase[c][i];
+                } else if (usingMidSide && channels == 2 &&
+                           c == 0 && inRange(f, guidance[1]->phaseReset)) {
+                    ph = phase[c][i];
                 } else if (inhop == outhop) {
                     ph = m_unlocked[c][i];
                 } else if (inRange (f, g->highUnlocked)) {
diff --git a/src/finer/R3Stretcher.cpp b/src/finer/R3Stretcher.cpp
index 3e1b9c8..bfbbbde 100644
--- a/src/finer/R3Stretcher.cpp
+++ b/src/finer/R3Stretcher.cpp
@@ -757,11 +757,13 @@ R3Stretcher::process(const float *const *input, size_t samples, bool final)
             int maxResampleInput = int(floor(maxResampleOutput * m_pitchScale));
             int resampleInput = std::min(remaining, maxResampleInput);
             if (resampleInput == 0) resampleInput = 1;
+
+            prepareInput(input, inputIx, resampleInput);
             
             int resampleOutput = m_resampler->resample
                 (m_channelAssembly.resampled.data(),
                  maxResampleOutput,
-                 input,
+                 m_channelAssembly.input.data(),
                  resampleInput,
                  1.0 / m_pitchScale,
                  final);
@@ -781,8 +783,11 @@ R3Stretcher::process(const float *const *input, size_t samples, bool final)
 
             m_log.log(2, "process: resamplingBefore is false, writing to inbuf from supplied data, former read space and samples being added", m_channelData[0]->inbuf->getReadSpace(), toWrite);
 
+            prepareInput(input, inputIx, toWrite);
+            
             for (int c = 0; c < m_parameters.channels; ++c) {
-                m_channelData[c]->inbuf->write(input[c] + inputIx, toWrite);
+                m_channelData[c]->inbuf->write
+                    (m_channelAssembly.input[c], toWrite);
             }
             inputIx += toWrite;
         }
@@ -819,9 +824,43 @@ R3Stretcher::retrieve(float *const *output, size_t samples) const
         }
     }
 
+    if (useMidSide()) {
+        for (int i = 0; i < got; ++i) {
+            float m = output[0][i];
+            float s = output[1][i];
+            float l = m + s;
+            float r = m - s;
+            output[0][i] = l;
+            output[1][i] = r;
+        }
+    }
+    
     return got;
 }
 
+void
+R3Stretcher::prepareInput(const float *const *input, int ix, int n)
+{
+    if (useMidSide()) {
+        auto &c0 = m_channelData.at(0)->mixdown;
+        auto &c1 = m_channelData.at(1)->mixdown;
+        for (int i = 0; i < n; ++i) {
+            float l = input[0][i + ix];
+            float r = input[1][i + ix];
+            float m = (l + r) / 2.f;
+            float s = (l - r) / 2.f;
+            c0[i] = m;
+            c1[i] = s;
+        }
+        m_channelAssembly.input[0] = m_channelData.at(0)->mixdown.data();
+        m_channelAssembly.input[1] = m_channelData.at(1)->mixdown.data();
+    } else {
+        for (int c = 0; c < m_parameters.channels; ++c) {
+            m_channelAssembly.input[c] = input[c] + ix;
+        }
+    }
+}
+
 void
 R3Stretcher::consume()
 {
@@ -933,6 +972,7 @@ R3Stretcher::consume()
                  m_channelAssembly.prevMag.data(),
                  m_guideConfiguration,
                  m_channelAssembly.guidance.data(),
+                 useMidSide(),
                  m_prevInhop,
                  m_prevOuthop);
         }
diff --git a/src/finer/R3Stretcher.h b/src/finer/R3Stretcher.h
index d1b8308..88660f1 100644
--- a/src/finer/R3Stretcher.h
+++ b/src/finer/R3Stretcher.h
@@ -241,7 +241,7 @@ protected:
                                BinClassifier::Classification::Residual),
             segmenter(new BinSegmenter(segmenterParameters)),
             segmentation(), prevSegmentation(), nextSegmentation(),
-            mixdown(longestFftSize, 0.f),
+            mixdown(inRingBufferSize, 0.f),
             resampled(outRingBufferSize, 0.f),
             inbuf(new RingBuffer<float>(inRingBufferSize)),
             outbuf(new RingBuffer<float>(outRingBufferSize)),
@@ -263,6 +263,7 @@ protected:
     struct ChannelAssembly {
         // Vectors of bare pointers, used to package container data
         // from different channels into arguments for PhaseAdvance
+        FixedVector<const float *> input;
         FixedVector<process_t *> mag;
         FixedVector<process_t *> phase;
         FixedVector<process_t *> prevMag;
@@ -271,6 +272,7 @@ protected:
         FixedVector<float *> mixdown;
         FixedVector<float *> resampled;
         ChannelAssembly(int channels) :
+            input(channels, nullptr),
             mag(channels, nullptr), phase(channels, nullptr),
             prevMag(channels, nullptr), guidance(channels, nullptr),
             outPhase(channels, nullptr), mixdown(channels, nullptr),
@@ -350,6 +352,7 @@ protected:
     };
     ProcessMode m_mode;
 
+    void prepareInput(const float *const *input, int ix, int n);
     void consume();
     void createResampler();
     void calculateHop();
@@ -469,6 +472,12 @@ protected:
         }
     }        
 
+    bool useMidSide() const {
+        return m_parameters.channels == 2 &&
+            (m_parameters.options &
+             RubberBandStretcher::OptionChannelsTogether);
+    }
+    
     bool isSingleWindowed() const {
         return m_parameters.options &
             RubberBandStretcher::OptionWindowShort;