diff --git a/src/effects/ChangeTempo.cpp b/src/effects/ChangeTempo.cpp
index 737a06109..bd9697853 100644
--- a/src/effects/ChangeTempo.cpp
+++ b/src/effects/ChangeTempo.cpp
@@ -51,6 +51,11 @@ EffectChangeTempo::EffectChangeTempo()
    m_ToLength = 0.0;	
 }
 
+double EffectChangeTempo::CalcPreviewInputLength(double previewLength)
+{
+   return previewLength * (100.0 + m_PercentChange) / 100.0;
+}
+
 wxString EffectChangeTempo::GetEffectDescription() { 
    // Note: This is useful only after change amount has been set. 
    return wxString::Format(_("Applied effect: %s %.1f%%"), 
diff --git a/src/effects/ChangeTempo.h b/src/effects/ChangeTempo.h
index 46ab36156..6a4454c67 100644
--- a/src/effects/ChangeTempo.h
+++ b/src/effects/ChangeTempo.h
@@ -59,6 +59,8 @@ class EffectChangeTempo : public EffectSoundTouch {
 
    virtual bool CheckWhetherSkipEffect() { return (m_PercentChange == 0.0); }
    virtual bool Process();
+
+   double CalcPreviewInputLength(double previewLength);
   
  private:
    double			m_PercentChange;	// percent change to apply to tempo
diff --git a/src/effects/Effect.cpp b/src/effects/Effect.cpp
index 372207a3f..9543b1e1d 100644
--- a/src/effects/Effect.cpp
+++ b/src/effects/Effect.cpp
@@ -403,6 +403,11 @@ long TrapLong(long x, long min, long max)
       return x;
 }
 
+double Effect::CalcPreviewInputLength(double previewLength)
+{
+   return previewLength;
+}
+
 wxString Effect::GetPreviewName()
 {
    return _("Pre&view");
@@ -417,12 +422,12 @@ void Effect::Preview()
    // Mix a few seconds of audio from all of the tracks
    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 + previewLen;
+   double t1 = t0 + CalcPreviewInputLength(previewLen);
 
    if (t1 > mT1)
       t1 = mT1;
@@ -488,6 +493,8 @@ void Effect::Preview()
       if (mixRight)
          playbackTracks.Add(mixRight);
 
+      t1 = wxMin(mixLeft->GetEndTime(), t0 + previewLen);
+
 #ifdef EXPERIMENTAL_MIDI_OUT
       NoteTrackArray empty;
 #endif
diff --git a/src/effects/Effect.h b/src/effects/Effect.h
index 9e2fa1148..ced330552 100644
--- a/src/effects/Effect.h
+++ b/src/effects/Effect.h
@@ -128,6 +128,10 @@ class AUDACITY_DLL_API Effect {
    // Only override it if you need to do preprocessing or cleanup.
    virtual void Preview();
 
+   // Most effects just use the previewLength, but time-stretching/compressing 
+   // effects need to use a different input length, so override this method. 
+   virtual double CalcPreviewInputLength(double previewLength);
+
    // Get an unique ID assigned to each registered effect.
    // The first effect will have ID zero.
    int GetID() {