diff --git a/src/effects/Amplify.cpp b/src/effects/Amplify.cpp
index 7d328b3ad..17c6abb53 100644
--- a/src/effects/Amplify.cpp
+++ b/src/effects/Amplify.cpp
@@ -66,6 +66,8 @@ EffectAmplify::EffectAmplify()
    mRatio = powf(10.0f, mAmp / 20.0f);
    mCanClip = false;
    mPeak = 0.0f;
+
+   SetLinearEffectFlag(true);
 }
 
 EffectAmplify::~EffectAmplify()
diff --git a/src/effects/AutoDuck.cpp b/src/effects/AutoDuck.cpp
index 4ec4dcb4d..7510d7b1e 100644
--- a/src/effects/AutoDuck.cpp
+++ b/src/effects/AutoDuck.cpp
@@ -90,6 +90,8 @@ EffectAutoDuck::EffectAutoDuck()
    mThresholdDb = DEF_ThresholdDb;
    mMaximumPause = DEF_MaximumPause;
 
+   SetLinearEffectFlag(true);
+
    mControlTrack = NULL;
 
    mPanel = NULL;
diff --git a/src/effects/BassTreble.cpp b/src/effects/BassTreble.cpp
index 858508167..1ff376016 100644
--- a/src/effects/BassTreble.cpp
+++ b/src/effects/BassTreble.cpp
@@ -76,6 +76,8 @@ EffectBassTreble::EffectBassTreble()
    dB_treble = DEF_Treble;
    dB_level = DEF_Level;
    mbNormalize = DEF_Normalize;
+
+   SetLinearEffectFlag(false);
 }
 
 EffectBassTreble::~EffectBassTreble()
diff --git a/src/effects/ChangePitch.cpp b/src/effects/ChangePitch.cpp
index 29d8eb894..ce3ad7c81 100644
--- a/src/effects/ChangePitch.cpp
+++ b/src/effects/ChangePitch.cpp
@@ -94,6 +94,8 @@ EffectChangePitch::EffectChangePitch()
 
    m_pTextCtrl_PercentChange = NULL;
    m_pSlider_PercentChange = NULL;
+
+   SetLinearEffectFlag(true);
 }
 
 EffectChangePitch::~EffectChangePitch()
diff --git a/src/effects/ChangeSpeed.cpp b/src/effects/ChangeSpeed.cpp
index 7209f2003..a7245b876 100644
--- a/src/effects/ChangeSpeed.cpp
+++ b/src/effects/ChangeSpeed.cpp
@@ -96,6 +96,8 @@ EffectChangeSpeed::EffectChangeSpeed()
    mToLength = 0.0;
    mFormat = _("hh:mm:ss + milliseconds");
    mbLoopDetect = false;
+
+   SetLinearEffectFlag(true);
 }
 
 EffectChangeSpeed::~EffectChangeSpeed()
diff --git a/src/effects/ChangeTempo.cpp b/src/effects/ChangeTempo.cpp
index 237ead6a8..31b841e85 100644
--- a/src/effects/ChangeTempo.cpp
+++ b/src/effects/ChangeTempo.cpp
@@ -70,6 +70,8 @@ EffectChangeTempo::EffectChangeTempo()
    m_ToLength = 0.0;
 
    m_bLoopDetect = false;
+
+   SetLinearEffectFlag(true);
 }
 
 EffectChangeTempo::~EffectChangeTempo()
diff --git a/src/effects/ClickRemoval.cpp b/src/effects/ClickRemoval.cpp
index b3a04558b..6b164dafa 100644
--- a/src/effects/ClickRemoval.cpp
+++ b/src/effects/ClickRemoval.cpp
@@ -61,6 +61,8 @@ EffectClickRemoval::EffectClickRemoval()
    mThresholdLevel = DEF_Threshold;
    mClickWidth = DEF_Width;
 
+   SetLinearEffectFlag(false);
+
    windowSize = 8192;
    sep = 2049;
 }
diff --git a/src/effects/Compressor.cpp b/src/effects/Compressor.cpp
index da7b26bc2..1c637daa8 100644
--- a/src/effects/Compressor.cpp
+++ b/src/effects/Compressor.cpp
@@ -85,6 +85,8 @@ EffectCompressor::EffectCompressor()
    mFollow1 = NULL;
    mFollow2 = NULL;
    mFollowLen = 0;
+
+   SetLinearEffectFlag(false);
 }
 
 EffectCompressor::~EffectCompressor()
diff --git a/src/effects/Echo.cpp b/src/effects/Echo.cpp
index 15a88a8ca..b956a4252 100644
--- a/src/effects/Echo.cpp
+++ b/src/effects/Echo.cpp
@@ -39,6 +39,8 @@ EffectEcho::EffectEcho()
 {
    delay = DEF_Delay;
    decay = DEF_Decay;
+
+   SetLinearEffectFlag(true);
 }
 
 EffectEcho::~EffectEcho()
diff --git a/src/effects/Effect.cpp b/src/effects/Effect.cpp
index a5fef5cc0..3564ccdfb 100644
--- a/src/effects/Effect.cpp
+++ b/src/effects/Effect.cpp
@@ -91,6 +91,7 @@ Effect::Effect()
    mT0 = 0.0;
    mT1 = 0.0;
    mDuration = 0.0;
+   mIsLinearEffect = false;
    mNumTracks = 0;
    mNumGroups = 0;
    mProgress = NULL;
@@ -759,6 +760,7 @@ void Effect::SetDuration(double seconds)
    }
 
    mDuration = seconds;
+   mSetDuration = mDuration;
 
    return;
 }
@@ -1931,6 +1933,11 @@ void Effect::EnableDebug(bool enable)
    mUIDebug = enable;
 }
 
+void Effect::SetLinearEffectFlag(bool linearEffectFlag)
+{
+   mIsLinearEffect = linearEffectFlag;
+}
+
 bool Effect::TotalProgress(double frac)
 {
    int updateResult = (mProgress ?
@@ -2352,6 +2359,11 @@ bool Effect::IsHidden()
 
 void Effect::Preview(bool dryOnly)
 {
+    if (mIsLinearEffect)
+       wxLogDebug(wxT("Linear Effect"));
+    else
+       wxLogDebug(wxT("Non-linear Effect"));
+
    if (mNumTracks==0) // nothing to preview
       return;
 
@@ -2363,46 +2375,81 @@ void Effect::Preview(bool dryOnly)
    double previewLen = 6.0;
    gPrefs->Read(wxT("/AudioIO/EffectsPreviewLen"), &previewLen);
 
-   WaveTrack *mixLeft = NULL;
-   WaveTrack *mixRight = NULL;
    double rate = mProjectRate;
    double t0 = mT0;
    double t1 = t0 + CalcPreviewInputLength(previewLen);
 
-   if (t1 > mT1)
-      t1 = mT1;
-
    // Generators can run without a selection.
-//   if (!GeneratorPreview() && (t1 <= t0))
-//      return;
-
-   bool success = ::MixAndRender(mTracks, mFactory, rate, floatSample, t0, t1,
-                                 &mixLeft, &mixRight);
-
-   if (!success) {
-      return;
+   if (GetType() == EffectTypeGenerate) {
+      // If a generator varies over time, it must use the selected duration.
+      // otherwise set it as a linear effect and process no more than the preview length.
+      // TODO: When previewing non-linear generate effect, calculate only the first 'preview length'.
+      double dur = (mIsLinearEffect)? wxMin(mSetDuration, CalcPreviewInputLength(previewLen)) : mSetDuration;
+      t1 = t0 + dur;
+      this->SetDuration(dur);
    }
+   else if (t1 > mT1) {
+      t1 = mT1;
+   }
+   if (t1 <= t0)
+      return;
+
+   bool success;
+   WaveTrack *mixLeft = NULL;
+   WaveTrack *mixRight = NULL;
 
    // Save the original track list
    TrackList *saveTracks = mTracks;
 
+   // Linear Effect preview optimised by pre-mixing to one track.
+   // Generators need to generate per track.
+   if (mIsLinearEffect && !(GetType() == EffectTypeGenerate)) {
+      success = ::MixAndRender(mTracks, mFactory, rate, floatSample, t0, t1,
+                               &mixLeft, &mixRight);
+   }
+
    // Build new tracklist from rendering tracks
    mTracks = new TrackList();
-   mixLeft->SetSelected(true);
-   mixLeft->SetDisplay(WaveTrack::NoDisplay);
-   mTracks->Add(mixLeft);
-   if (mixRight) {
-      mixRight->SetSelected(true);
-      mTracks->Add(mixRight);
+
+   if (mIsLinearEffect && !(GetType() == EffectTypeGenerate)) {
+      if (!success) {
+         delete mTracks;
+         mTracks = saveTracks;
+         return;
+      }
+
+      mixLeft->SetSelected(true);
+      mixLeft->SetDisplay(WaveTrack::NoDisplay);
+      mTracks->Add(mixLeft);
+      if (mixRight) {
+         mixRight->SetSelected(true);
+         mTracks->Add(mixRight);
+      }
+
+      // TODO:  Don't really think this is necessary, but doesn't hurt
+      // Reset times
+      t0 = mixLeft->GetStartTime();
+      t1 = mixLeft->GetEndTime();
+   }
+   else {
+      // Copy all tracks as 'some' effects (AutoDuck) may require non-selected tracks.
+      TrackListOfKindIterator iter(Track::Wave, saveTracks);
+      WaveTrack *src = (WaveTrack *) iter.First();
+      while (src)
+      {
+         WaveTrack *dest;
+         src->Copy(t0, t1, (Track **) &dest);
+         dest->SetSelected(src->GetSelected());
+         dest->SetDisplay(WaveTrack::NoDisplay);
+         mTracks->Add(dest);
+
+         src = (WaveTrack *) iter.Next();
+      }
    }
 
    // Update track/group counts
    CountWaveTracks();
 
-   // Reset times
-   t0 = mixLeft->GetStartTime();
-   t1 = mixLeft->GetEndTime();
-
    double t0save = mT0;
    double t1save = mT1;
    mT0 = t0;
@@ -2412,36 +2459,26 @@ void Effect::Preview(bool dryOnly)
 
    bool bSuccess(true);
    if (!dryOnly) {
-      // Effect is already inited; we call Process, End, and then Init
-      // again, so the state is exactly the way it was before Preview
-      // was called.
       mProgress = new ProgressDialog(GetName(),
             _("Preparing preview"),
             pdlgHideCancelButton); // Have only "Stop" button.
       bSuccess = Process();
       delete mProgress;
       mProgress = NULL;
-      End();
-      Init();
    }
 
-   // Restore original selection
-   mT0 = t0save;
-   mT1 = t1save;
-
    if (bSuccess)
    {
       WaveTrackArray playbackTracks;
       WaveTrackArray recordingTracks;
-      // Probably not the same tracks post-processing, so can't rely on previous values of mixLeft & mixRight.
-      TrackListOfKindIterator iter(Track::Wave, mTracks);
-      mixLeft = (WaveTrack*)(iter.First());
-      mixRight = (WaveTrack*)(iter.Next());
-      playbackTracks.Add(mixLeft);
-      if (mixRight)
-         playbackTracks.Add(mixRight);
 
-      t1 = wxMin(mixLeft->GetEndTime(), t0 + previewLen);
+      SelectedTrackListOfKindIterator iter(Track::Wave, mTracks);
+      WaveTrack *src = (WaveTrack *) iter.First();
+      while (src)
+      {
+         playbackTracks.Add(src);
+         src = (WaveTrack *) iter.Next();
+      }
 
 #ifdef EXPERIMENTAL_MIDI_OUT
       NoteTrackArray empty;
@@ -2452,17 +2489,17 @@ void Effect::Preview(bool dryOnly)
 #ifdef EXPERIMENTAL_MIDI_OUT
                                empty,
 #endif
-                               rate, t0, t1);
+                               rate, mT0, mT1);
 
       if (token) {
          int previewing = eProgressSuccess;
 
          mProgress = new ProgressDialog(GetName(),
-                                        _("Previewing"), pdlgHideCancelButton);
+                                       _("Previewing"), pdlgHideCancelButton);
 
          while (gAudioIO->IsStreamActive(token) && previewing == eProgressSuccess) {
             ::wxMilliSleep(100);
-            previewing = mProgress->Update(gAudioIO->GetStreamTime() - t0, t1 - t0);
+            previewing = mProgress->Update(gAudioIO->GetStreamTime() - mT0, mT1);
          }
          gAudioIO->StopStream();
 
@@ -2475,10 +2512,14 @@ void Effect::Preview(bool dryOnly)
       }
       else {
          wxMessageBox(_("Error while opening sound device. Please check the playback device settings and the project sample rate."),
-                      _("Error"), wxOK | wxICON_EXCLAMATION, FocusDialog);
+                     _("Error"), wxOK | wxICON_EXCLAMATION, FocusDialog);
       }
    }
 
+   // Restore original selection
+   mT0 = t0save;
+   mT1 = t1save;
+
    if (FocusDialog) {
       FocusDialog->SetFocus();
    }
@@ -2490,6 +2531,13 @@ void Effect::Preview(bool dryOnly)
    delete mTracks;
 
    mTracks = saveTracks;
+   // Effect is already inited; we call Process, End, and then Init
+   // again, so the state is exactly the way it was before Preview
+   // was called.
+   if (!dryOnly) {
+      End();
+      Init();
+   }
 }
 
 BEGIN_EVENT_TABLE(EffectDialog, wxDialog)
diff --git a/src/effects/Effect.h b/src/effects/Effect.h
index 2c08a716c..38a61f0c4 100644
--- a/src/effects/Effect.h
+++ b/src/effects/Effect.h
@@ -316,6 +316,11 @@ protected:
    void SetTimeWarper(TimeWarper *warper);
    TimeWarper *GetTimeWarper();
 
+   // Previewing linear effect can be optimised by pre-mixing. However this
+   // should not be used for non-linear effects such as dynamic processors
+   // To allow pre-mixing before Preview, set linearEffectFlag to true.
+   void SetLinearEffectFlag(bool linearEffectFlag);
+
    // Use these two methods to copy the input tracks to mOutputTracks, if
    // doing the processing on them, and replacing the originals only on success (and not cancel).
    void CopyInputTracks(int trackType = Track::Wave);
@@ -388,7 +393,11 @@ private:
 
    bool mIsBatch;
 
+   bool mIsLinearEffect;
+
    double mDuration;
+   // mSetDuration should ONLY be set when SetDuration() is called.
+   double mSetDuration;
 
    bool mUIDebug;
 
diff --git a/src/effects/Equalization.cpp b/src/effects/Equalization.cpp
index 55b1ac483..733bed756 100644
--- a/src/effects/Equalization.cpp
+++ b/src/effects/Equalization.cpp
@@ -217,6 +217,8 @@ EffectEqualization::EffectEqualization()
    mFilterFuncR = new float[windowSize];
    mFilterFuncI = new float[windowSize];
 
+   SetLinearEffectFlag(true);
+
 #ifdef EXPERIMENTAL_EQ_SSE_THREADED
    mEffectEqualization48x=NULL;
 #endif
diff --git a/src/effects/Noise.cpp b/src/effects/Noise.cpp
index 2b19a43b3..0b648980e 100644
--- a/src/effects/Noise.cpp
+++ b/src/effects/Noise.cpp
@@ -57,6 +57,8 @@ EffectNoise::EffectNoise()
    mType = DEF_Type;
    mAmp = DEF_Amp;
 
+   SetLinearEffectFlag(true);
+
    y = z = buf0 = buf1 = buf2 = buf3 = buf4 = buf5 = buf6 = 0;
 }
 
diff --git a/src/effects/Normalize.cpp b/src/effects/Normalize.cpp
index bf1fdb53b..51d486ca1 100644
--- a/src/effects/Normalize.cpp
+++ b/src/effects/Normalize.cpp
@@ -49,6 +49,8 @@ EffectNormalize::EffectNormalize()
    mDC = DEF_RemoveDC;
    mGain = DEF_ApplyGain;
    mStereoInd = DEF_StereoInd;
+
+   SetLinearEffectFlag(false);
 }
 
 EffectNormalize::~EffectNormalize()
diff --git a/src/effects/Paulstretch.cpp b/src/effects/Paulstretch.cpp
index 1c8084497..e2e7f77cd 100644
--- a/src/effects/Paulstretch.cpp
+++ b/src/effects/Paulstretch.cpp
@@ -79,6 +79,8 @@ EffectPaulstretch::EffectPaulstretch()
 {
    amount = DEF_Amount;
    time_resolution = DEF_Time;
+
+   SetLinearEffectFlag(true);
 }
 
 EffectPaulstretch::~EffectPaulstretch()
diff --git a/src/effects/Phaser.cpp b/src/effects/Phaser.cpp
index 63609d395..c3bc2425b 100644
--- a/src/effects/Phaser.cpp
+++ b/src/effects/Phaser.cpp
@@ -82,6 +82,8 @@ EffectPhaser::EffectPhaser()
    mPhase = DEF_Phase;
    mDepth = DEF_Depth;
    mFeedback = DEF_Feedback;
+
+   SetLinearEffectFlag(true);
 }
 
 EffectPhaser::~EffectPhaser()
diff --git a/src/effects/Repeat.cpp b/src/effects/Repeat.cpp
index ac44afcb7..62b2a59ba 100644
--- a/src/effects/Repeat.cpp
+++ b/src/effects/Repeat.cpp
@@ -47,6 +47,8 @@ END_EVENT_TABLE()
 EffectRepeat::EffectRepeat()
 {
    repeatCount = 10;
+
+   SetLinearEffectFlag(true);
 }
 
 EffectRepeat::~EffectRepeat()
diff --git a/src/effects/Reverb.cpp b/src/effects/Reverb.cpp
index 5129d9eb6..7ccd3e9e1 100644
--- a/src/effects/Reverb.cpp
+++ b/src/effects/Reverb.cpp
@@ -119,6 +119,8 @@ EffectReverb::EffectReverb()
    mParams.mWetOnly = DEF_WetOnly;
 
    mProcessingEvent = false;
+
+   SetLinearEffectFlag(true);
 }
 
 EffectReverb::~EffectReverb()
diff --git a/src/effects/ScienFilter.cpp b/src/effects/ScienFilter.cpp
index e65d965ec..620bce04b 100644
--- a/src/effects/ScienFilter.cpp
+++ b/src/effects/ScienFilter.cpp
@@ -160,6 +160,8 @@ EffectScienFilter::EffectScienFilter()
    mRipple = DEF_Passband;
    mStopbandRipple = DEF_Stopband;
 
+   SetLinearEffectFlag(true);
+
    mOrderIndex = mOrder - 1;
 
    mdBMin = -30.0;
diff --git a/src/effects/Silence.cpp b/src/effects/Silence.cpp
index 490941db1..00f2306fe 100644
--- a/src/effects/Silence.cpp
+++ b/src/effects/Silence.cpp
@@ -21,6 +21,7 @@
 
 EffectSilence::EffectSilence()
 {
+   SetLinearEffectFlag(true);
 }
 
 EffectSilence::~EffectSilence()
diff --git a/src/effects/TimeScale.cpp b/src/effects/TimeScale.cpp
index e370bdb92..c14609752 100644
--- a/src/effects/TimeScale.cpp
+++ b/src/effects/TimeScale.cpp
@@ -69,6 +69,8 @@ EffectTimeScale::EffectTimeScale()
    m_PitchHalfStepsEnd = DEF_HalfStepsEnd;
    m_PitchPercentChangeStart = DEF_PitchPercentStart;
    m_PitchPercentChangeEnd = DEF_PitchPercentEnd;
+
+   SetLinearEffectFlag(true);
 }
 
 EffectTimeScale::~EffectTimeScale()
diff --git a/src/effects/ToneGen.cpp b/src/effects/ToneGen.cpp
index fba98a3d2..66a1c7a51 100644
--- a/src/effects/ToneGen.cpp
+++ b/src/effects/ToneGen.cpp
@@ -105,6 +105,12 @@ EffectToneGen::EffectToneGen(bool isChirp)
    {
       mInterpolations.Add(wxGetTranslation(kInterStrings[i]));
    }
+   // Chirp varies over time so must use selected duration.
+   // TODO: When previewing, calculate only the first 'preview length'.
+   if (isChirp)
+      SetLinearEffectFlag(false);
+   else
+      SetLinearEffectFlag(true);
 }
 
 EffectToneGen::~EffectToneGen()
diff --git a/src/effects/TruncSilence.cpp b/src/effects/TruncSilence.cpp
index 279c4a122..b29d20c3e 100644
--- a/src/effects/TruncSilence.cpp
+++ b/src/effects/TruncSilence.cpp
@@ -76,6 +76,8 @@ EffectTruncSilence::EffectTruncSilence()
    mTruncDbChoiceIndex = DEF_DbIndex;
    mActionIndex = DEF_ActIndex;
 
+   SetLinearEffectFlag(false);
+
    // This used to be changeable via the audacity.cfg/registery.  Doubtful that was
    // ever done.
    //
diff --git a/src/effects/Wahwah.cpp b/src/effects/Wahwah.cpp
index 05a76af2c..3d81e487c 100644
--- a/src/effects/Wahwah.cpp
+++ b/src/effects/Wahwah.cpp
@@ -73,6 +73,8 @@ EffectWahwah::EffectWahwah()
    mDepth = DEF_Depth;
    mRes = DEF_Res;
    mFreqOfs = DEF_FreqOfs;
+
+   SetLinearEffectFlag(true);
 }
 
 EffectWahwah::~EffectWahwah()