diff --git a/src/commands/AudacityCommand.cpp b/src/commands/AudacityCommand.cpp
index a47cb1bec..fbe31281c 100644
--- a/src/commands/AudacityCommand.cpp
+++ b/src/commands/AudacityCommand.cpp
@@ -168,12 +168,9 @@ bool AudacityCommand::SetAutomationParameters(const wxString & parms)
    if (!S.bOK)
    {
       AudacityCommand::MessageBox(
-         wxString::Format(
-            _("%s: Could not load settings below. Default settings will be used.\n\n%s"),
-            GetName().Translation(),
-            preset
-         )
-      );
+         XO(
+"%s: Could not load settings below. Default settings will be used.\n\n%s")
+            .Format( GetName(), preset ) );
 
       // fror now always succeed, so that we can prompt the user.
       return true;
@@ -241,14 +238,15 @@ bool AudacityCommand::TransferDataFromWindow()
    return true;
 }
 
-int AudacityCommand::MessageBox(const wxString& message, long style, const wxString &titleStr)
+int AudacityCommand::MessageBox(
+   const TranslatableString& message, long style,
+   const TranslatableString &titleStr)
 {
-   wxString title;
-   if (titleStr.empty())
-      title = GetName().Translation();
-   else
-      title = wxString::Format(_("%s: %s"), GetName().Translation(), titleStr);
-   return AudacityMessageBox(message, title, style, mUIParent);
+   auto title = titleStr.empty()
+      ? GetName()
+      : XO("%s: %s").Format( GetName(), titleStr );
+   return AudacityMessageBox(
+      message.Translation(), title.Translation(), style, mUIParent);
 }
 
 BEGIN_EVENT_TABLE(AudacityCommandDialog, wxDialogWrapper)
diff --git a/src/commands/AudacityCommand.h b/src/commands/AudacityCommand.h
index 2407254a2..ae5ff6f66 100644
--- a/src/commands/AudacityCommand.h
+++ b/src/commands/AudacityCommand.h
@@ -86,9 +86,9 @@ class AUDACITY_DLL_API AudacityCommand /* not final */ : public wxEvtHandler,
    // Display a message box, using effect's (translated) name as the prefix
    // for the title.
    enum : long { DefaultMessageBoxStyle = wxOK | wxCENTRE };
-   int MessageBox(const wxString& message,
+   int MessageBox(const TranslatableString& message,
                   long style = DefaultMessageBoxStyle,
-                  const wxString& titleStr = wxString{});
+                  const TranslatableString& titleStr = {});
 
 //
 // protected virtual methods
diff --git a/src/effects/AutoDuck.cpp b/src/effects/AutoDuck.cpp
index e7870e58e..fb5878305 100644
--- a/src/effects/AutoDuck.cpp
+++ b/src/effects/AutoDuck.cpp
@@ -228,11 +228,11 @@ bool EffectAutoDuck::Init()
             },
             [&](const Track *) {
                Effect::MessageBox(
-                  _("You selected a track which does not contain audio. AutoDuck can only process audio tracks."),
                   /* i18n-hint: Auto duck is the name of an effect that 'ducks' (reduces the volume)
                    * of the audio automatically when there is sound on another track.  Not as
                    * in 'Donald-Duck'!*/
-                  wxICON_ERROR);
+                  XO("You selected a track which does not contain audio. AutoDuck can only process audio tracks."),
+                  wxICON_ERROR );
                return false;
             }
          );
@@ -244,8 +244,11 @@ bool EffectAutoDuck::Init()
    if (!controlTrackCandidate)
    {
       Effect::MessageBox(
-         _("Auto Duck needs a control track which must be placed below the selected track(s)."),
-         wxICON_ERROR);
+         /* i18n-hint: Auto duck is the name of an effect that 'ducks' (reduces the volume)
+          * of the audio automatically when there is sound on another track.  Not as
+          * in 'Donald-Duck'!*/
+         XO("Auto Duck needs a control track which must be placed below the selected track(s)."),
+         wxICON_ERROR );
       return false;
    }
 
diff --git a/src/effects/ClickRemoval.cpp b/src/effects/ClickRemoval.cpp
index ebb6ea6e3..7ced5f8e5 100644
--- a/src/effects/ClickRemoval.cpp
+++ b/src/effects/ClickRemoval.cpp
@@ -197,8 +197,8 @@ bool EffectClickRemoval::Process()
    }
    if (bGoodResult && !mbDidSomething) // Processing successful, but ineffective.
       Effect::MessageBox(
-         _("Algorithm not effective on this audio. Nothing changed."),
-         wxOK | wxICON_ERROR);
+         XO("Algorithm not effective on this audio. Nothing changed."),
+         wxOK | wxICON_ERROR );
 
    this->ReplaceProcessedTracks(bGoodResult && mbDidSomething);
    return bGoodResult && mbDidSomething;
@@ -209,9 +209,9 @@ bool EffectClickRemoval::ProcessOne(int count, WaveTrack * track, sampleCount st
    if (len <= windowSize / 2)
    {
       Effect::MessageBox(
-         wxString::Format(_("Selection must be larger than %d samples."),
-                          windowSize / 2),
-         wxOK | wxICON_ERROR);
+         XO("Selection must be larger than %d samples.")
+            .Format(windowSize / 2),
+         wxOK | wxICON_ERROR );
       return false;
    }
 
diff --git a/src/effects/Echo.cpp b/src/effects/Echo.cpp
index 590c7859c..b9b6fef53 100644
--- a/src/effects/Echo.cpp
+++ b/src/effects/Echo.cpp
@@ -105,7 +105,7 @@ bool EffectEcho::ProcessInitialize(sampleCount WXUNUSED(totalLen), ChannelNames
       history.reinit(histLen, true);
    }
    catch ( const std::bad_alloc& ) {
-      Effect::MessageBox(_("Requested value exceeds memory capacity."));
+      Effect::MessageBox( XO("Requested value exceeds memory capacity.") );
       return false;
    }
 
diff --git a/src/effects/Effect.cpp b/src/effects/Effect.cpp
index c8e08df5f..dd3a46062 100644
--- a/src/effects/Effect.cpp
+++ b/src/effects/Effect.cpp
@@ -1081,12 +1081,8 @@ bool Effect::SetAutomationParameters(const wxString & parms)
    if (!success)
    {
       Effect::MessageBox(
-         wxString::Format(
-            _("%s: Could not load settings below. Default settings will be used.\n\n%s"),
-            GetName().Translation(),
-            preset
-         )
-      );
+         XO("%s: Could not load settings below. Default settings will be used.\n\n%s")
+            .Format( GetName(), preset ) );
       // We are using defualt settings and we still wish to continue.
       return true;
       //return false;
@@ -2451,15 +2447,14 @@ void Effect::Preview(bool dryOnly)
    }
 }
 
-int Effect::MessageBox
-(const wxString& message, long style, const wxString &titleStr)
+int Effect::MessageBox( const TranslatableString& message,
+   long style, const TranslatableString &titleStr)
 {
-   wxString title;
-   if (titleStr.empty())
-      title = GetName().Translation();
-   else
-      title = wxString::Format(_("%s: %s"), GetName().Translation(), titleStr);
-   return AudacityMessageBox(message, title, style, mUIParent);
+   auto title = titleStr.empty()
+      ? GetName()
+      : XO("%s: %s").Format( GetName(), titleStr );
+   return AudacityMessageBox(
+      message.Translation(), title.Translation(), style, mUIParent );
 }
 
 BEGIN_EVENT_TABLE(EffectDialog, wxDialogWrapper)
diff --git a/src/effects/Effect.h b/src/effects/Effect.h
index 1be5d4aef..f6f146ad0 100644
--- a/src/effects/Effect.h
+++ b/src/effects/Effect.h
@@ -269,9 +269,9 @@ class AUDACITY_DLL_API Effect /* not final */ : public wxEvtHandler,
    // Display a message box, using effect's (translated) name as the prefix
    // for the title.
    enum : long { DefaultMessageBoxStyle = wxOK | wxCENTRE };
-   int MessageBox(const wxString& message,
+   int MessageBox(const TranslatableString& message,
                   long style = DefaultMessageBoxStyle,
-                  const wxString& titleStr = wxString{});
+                  const TranslatableString& titleStr = {});
 
    static void IncEffectCounter(){ nEffectsDone++;};
 
diff --git a/src/effects/Equalization.cpp b/src/effects/Equalization.cpp
index 89fa1d909..2a270bb8e 100644
--- a/src/effects/Equalization.cpp
+++ b/src/effects/Equalization.cpp
@@ -505,9 +505,10 @@ bool EffectEqualization::ValidateUI()
    {
       // PRL:  This is unreachable.  mDisallowCustom is always false.
 
-      Effect::MessageBox(_("To use this filter curve in a macro, please choose a new name for it.\nChoose the 'Save/Manage Curves...' button and rename the 'unnamed' curve, then use that one."),
+      Effect::MessageBox(
+         XO("To use this filter curve in a macro, please choose a new name for it.\nChoose the 'Save/Manage Curves...' button and rename the 'unnamed' curve, then use that one."),
          wxOK | wxCENTRE,
-         _("Filter Curve needs a different name"));
+         XO("Filter Curve needs a different name") );
       return false;
    }
 
@@ -626,7 +627,9 @@ bool EffectEqualization::Init()
 
       for (auto track : trackRange) {
          if (track->GetRate() != rate) {
-            Effect::MessageBox(_("To apply Equalization, all selected tracks must have the same sample rate."));
+            Effect::MessageBox(
+               XO(
+"To apply Equalization, all selected tracks must have the same sample rate.") );
             return(false);
          }
          ++selcount;
@@ -636,9 +639,10 @@ bool EffectEqualization::Init()
    mHiFreq = rate / 2.0;
    // Unlikely, but better than crashing.
    if (mHiFreq <= loFreqI) {
-      Effect::MessageBox( _("Track sample rate is too low for this effect."),
-                    wxOK | wxCENTRE,
-                    _("Effect Unavailable"));
+      Effect::MessageBox(
+         XO("Track sample rate is too low for this effect."),
+         wxOK | wxCENTRE,
+         XO("Effect Unavailable") );
       return(false);
    }
 
@@ -1601,13 +1605,15 @@ void EffectEqualization::LoadCurves(const wxString &fileName, bool append)
    const wxString fullPath{ fn.GetFullPath() };
    if( !reader.Parse( this, fullPath ) )
    {
-      wxString msg;
       /* i18n-hint: EQ stands for 'Equalization'.*/
-      msg.Printf(_("Error Loading EQ Curves from file:\n%s\nError message says:\n%s"), fullPath, reader.GetErrorStr());
+      auto msg = XO(
+"Error Loading EQ Curves from file:\n%s\nError message says:\n%s")
+         .Format( fullPath, reader.GetErrorStr() );
       // Inform user of load failure
-      Effect::MessageBox( msg,
+      Effect::MessageBox(
+         msg,
          wxOK | wxCENTRE,
-         _("Error Loading EQ Curves"));
+         XO("Error Loading EQ Curves") );
       mCurves.push_back( _("unnamed") );  // we always need a default curve to use
       return;
    }
@@ -2002,9 +2008,10 @@ void EffectEqualization::setCurve(const wxString &curveName)
          break;
    if( i == mCurves.size())
    {
-      Effect::MessageBox( _("Requested curve not found, using 'unnamed'"),
+      Effect::MessageBox(
+         XO("Requested curve not found, using 'unnamed'"),
          wxOK|wxICON_ERROR,
-         _("Curve not found") );
+         XO("Curve not found") );
       setCurve();
    }
    else
@@ -3411,9 +3418,10 @@ void EditCurvesDialog::OnUp(wxCommandEvent & WXUNUSED(event))
    {
       if ( item == mList->GetItemCount()-1)
       {  // 'unnamed' always stays at the bottom
-         mEffect->Effect::MessageBox(_("'unnamed' always stays at the bottom of the list"),
-                            Effect::DefaultMessageBoxStyle,
-                            _("'unnamed' is special"));   // these could get tedious!
+         mEffect->Effect::MessageBox(
+            XO("'unnamed' always stays at the bottom of the list"),
+            Effect::DefaultMessageBoxStyle,
+            XO("'unnamed' is special") );   // these could get tedious!
          return;
       }
       state = mList->GetItemState(item-1, wxLIST_STATE_SELECTED);
@@ -3533,12 +3541,16 @@ void EditCurvesDialog::OnRename(wxCommandEvent & WXUNUSED(event))
                bad = true;
                if( curve == item )  // trying to rename a curve with the same name
                {
-                  mEffect->Effect::MessageBox( _("Name is the same as the original one"), wxOK, _("Same name") );
+                  mEffect->Effect::MessageBox(
+                     XO("Name is the same as the original one"),
+                     wxOK,
+                     XO("Same name") );
                   break;
                }
                int answer = mEffect->Effect::MessageBox(
-                  wxString::Format( _("Overwrite existing curve '%s'?"), name ),
-                  wxYES_NO, _("Curve exists") );
+                  XO("Overwrite existing curve '%s'?").Format( name ),
+                  wxYES_NO,
+                  XO("Curve exists") );
                if (answer == wxYES)
                {
                   bad = false;
@@ -3609,18 +3621,22 @@ void EditCurvesDialog::OnDelete(wxCommandEvent & WXUNUSED(event))
    {
       if(item == mList->GetItemCount()-1)   //unnamed
       {
-         mEffect->Effect::MessageBox(_("You cannot delete the 'unnamed' curve."),
-             wxOK | wxCENTRE, _("Can't delete 'unnamed'"));
+         mEffect->Effect::MessageBox(
+            XO("You cannot delete the 'unnamed' curve."),
+            wxOK | wxCENTRE,
+            XO("Can't delete 'unnamed'") );
       }
       else
       {
          // Create the prompt
-         wxString quest;
-         quest = wxString::Format(_("Delete '%s'?"),
-                                  mEditCurves[ item-deleted ].Name);
+         auto quest = XO("Delete '%s'?")
+            .Format(mEditCurves[ item-deleted ].Name));
 
          // Ask for confirmation before removal
-         int ans = mEffect->Effect::MessageBox( quest, wxYES_NO | wxCENTRE, _("Confirm Deletion") );
+         int ans = mEffect->Effect::MessageBox(
+            quest,
+            wxYES_NO | wxCENTRE,
+            XO("Confirm Deletion") );
          if( ans == wxYES )
          {  // Remove the curve from the array
             mEditCurves.RemoveAt( item-deleted );
@@ -3641,16 +3657,19 @@ void EditCurvesDialog::OnDelete(wxCommandEvent & WXUNUSED(event))
    int count = mList->GetSelectedItemCount();
    long item = mList->GetNextItem(-1, wxLIST_NEXT_ALL, wxLIST_STATE_SELECTED);
    // Create the prompt
-   wxString quest;
+   TranslatableString quest;
    if( count > 1 )
-      quest = wxString::Format(_("Delete %d items?"), count);
+      quest = XO("Delete %d items?").Format( count );
    else
       if( count == 1 )
-         quest = wxString::Format(_("Delete '%s'?"), mEditCurves[ item ].Name);
+         quest = XO("Delete '%s'?").Format( mEditCurves[ item ].Name );
       else
          return;
    // Ask for confirmation before removal
-   int ans = mEffect->Effect::MessageBox( quest, wxYES_NO | wxCENTRE, _("Confirm Deletion") );
+   int ans = mEffect->Effect::MessageBox(
+      quest,
+      wxYES_NO | wxCENTRE,
+      XO("Confirm Deletion") );
    if( ans == wxYES )
    {  // Remove the curve(s) from the array
       // Take care, mList and mEditCurves will get out of sync as curves are deleted
@@ -3660,9 +3679,10 @@ void EditCurvesDialog::OnDelete(wxCommandEvent & WXUNUSED(event))
          // TODO: Migrate to the standard "Manage" dialog.
          if(item == mList->GetItemCount()-1)   //unnamed
          {
-            mEffect->Effect::MessageBox(_("You cannot delete the 'unnamed' curve, it is special."),
-                                        Effect::DefaultMessageBoxStyle,
-                                        _("Can't delete 'unnamed'"));
+            mEffect->Effect::MessageBox(
+               XO("You cannot delete the 'unnamed' curve, it is special."),
+               Effect::DefaultMessageBoxStyle,
+               XO("Can't delete 'unnamed'") );
          }
          else
          {
@@ -3724,9 +3744,10 @@ void EditCurvesDialog::OnExport( wxCommandEvent & WXUNUSED(event))
          i++;
       }
       else
-         mEffect->Effect::MessageBox(_("You cannot export 'unnamed' curve, it is special."),
-                            Effect::DefaultMessageBoxStyle,
-                            _("Cannot Export 'unnamed'"));
+         mEffect->Effect::MessageBox(
+            XO("You cannot export 'unnamed' curve, it is special."),
+            Effect::DefaultMessageBoxStyle,
+            XO("Cannot Export 'unnamed'") );
       // get next selected item
       item = mList->GetNextItem(item, wxLIST_NEXT_ALL, wxLIST_STATE_SELECTED);
    }
@@ -3735,16 +3756,17 @@ void EditCurvesDialog::OnExport( wxCommandEvent & WXUNUSED(event))
       mEffect->mCurves = exportCurves;
       mEffect->SaveCurves(fileName);
       mEffect->mCurves = temp;
-      wxString message;
-      message.Printf(_("%d curves exported to %s"), i, fileName);
-      mEffect->Effect::MessageBox(message,
-                                  Effect::DefaultMessageBoxStyle,
-                                  _("Curves exported"));
+      auto message = XO("%d curves exported to %s").Format( i, fileName );
+      mEffect->Effect::MessageBox(
+         message,
+         Effect::DefaultMessageBoxStyle,
+         XO("Curves exported") );
    }
    else
-      mEffect->Effect::MessageBox(_("No curves exported"),
-                                  Effect::DefaultMessageBoxStyle,
-                                  _("No curves exported"));
+      mEffect->Effect::MessageBox(
+         XO("No curves exported"),
+         Effect::DefaultMessageBoxStyle,
+         XO("No curves exported") );
 }
 
 void EditCurvesDialog::OnLibrary( wxCommandEvent & WXUNUSED(event))
diff --git a/src/effects/Equalization48x.cpp b/src/effects/Equalization48x.cpp
index ffa7467e8..ccd96d598 100644
--- a/src/effects/Equalization48x.cpp
+++ b/src/effects/Equalization48x.cpp
@@ -500,8 +500,14 @@ bool EffectEqualization48x::Benchmark(EffectEqualization* effectEqualization)
    wxTimeSpan tsDefault(0, 0, 0, times[4]);
 
    mEffectEqualization->MessageBox(
-      wxString::Format(_("Benchmark times:\nOriginal: %s\nDefault Segmented: %s\nDefault Threaded: %s\nSSE: %s\nSSE Threaded: %s\n"),tsDefault.Format(wxT("%M:%S.%l")),
-      tsDefaultEnhanced.Format(wxT("%M:%S.%l")), tsDefaultThreaded.Format(wxT("%M:%S.%l")),tsSSE.Format(wxT("%M:%S.%l")),tsSSEThreaded.Format(wxT("%M:%S.%l"))));
+      XO(
+"Benchmark times:\nOriginal: %s\nDefault Segmented: %s\nDefault Threaded: %s\nSSE: %s\nSSE Threaded: %s\n")
+         .Format(
+            tsDefault.Format(wxT("%M:%S.%l")),
+            tsDefaultEnhanced.Format(wxT("%M:%S.%l")),
+            tsDefaultThreaded.Format(wxT("%M:%S.%l")),
+            tsSSE.Format(wxT("%M:%S.%l")),
+            tsSSEThreaded.Format(wxT("%M:%S.%l")) ) );
    return bBreakLoop; // return !bBreakLoop ?
 }
 
diff --git a/src/effects/FindClipping.cpp b/src/effects/FindClipping.cpp
index e4acfad23..0a7594c3e 100644
--- a/src/effects/FindClipping.cpp
+++ b/src/effects/FindClipping.cpp
@@ -171,7 +171,7 @@ bool EffectFindClipping::ProcessOne(LabelTrack * lt,
       buffer.reinit(blockSize);
    }
    catch( const std::bad_alloc & ) {
-      Effect::MessageBox(_("Requested value exceeds memory capacity."));
+      Effect::MessageBox( XO("Requested value exceeds memory capacity.") );
       return false;
    }
 
diff --git a/src/effects/Generator.cpp b/src/effects/Generator.cpp
index 8f4d8e640..5be73c8ed 100644
--- a/src/effects/Generator.cpp
+++ b/src/effects/Generator.cpp
@@ -52,9 +52,9 @@ bool Generator::Process()
              !track->IsEmpty(mT0, mT0+GetDuration()-(mT1-mT0)-1.0/track->GetRate()))
          {
             Effect::MessageBox(
-                  _("There is not enough room available to generate the audio"),
-                  wxICON_STOP,
-                  _("Error"));
+               XO("There is not enough room available to generate the audio"),
+               wxICON_STOP,
+               XO("Error") );
             Failure();
             bGoodResult = false;
             return;
diff --git a/src/effects/NoiseReduction.cpp b/src/effects/NoiseReduction.cpp
index a873ea887..6bc0d5025 100644
--- a/src/effects/NoiseReduction.cpp
+++ b/src/effects/NoiseReduction.cpp
@@ -586,17 +586,21 @@ bool EffectNoiseReduction::Settings::PrefsIO(bool read)
 bool EffectNoiseReduction::Settings::Validate(EffectNoiseReduction *effect) const
 {
    if (StepsPerWindow() < windowTypesInfo[mWindowTypes].minSteps) {
-      effect->Effect::MessageBox(_("Steps per block are too few for the window types."));
+      effect->Effect::MessageBox(
+         XO("Steps per block are too few for the window types.") );
       return false;
    }
 
    if (StepsPerWindow() > WindowSize()) {
-      effect->Effect::MessageBox(_("Steps per block cannot exceed the window size."));
+      effect->Effect::MessageBox(
+         XO("Steps per block cannot exceed the window size.") );
       return false;
    }
 
    if (mMethod == DM_MEDIAN && StepsPerWindow() > 4) {
-      effect->Effect::MessageBox(_("Median method is not implemented for more than four steps per window."));
+      effect->Effect::MessageBox(
+         XO(
+"Median method is not implemented for more than four steps per window.") );
       return false;
    }
 
@@ -622,12 +626,14 @@ bool EffectNoiseReduction::Process()
    }
    else if (mStatistics->mWindowSize != mSettings->WindowSize()) {
       // possible only with advanced settings
-      ::Effect::MessageBox(_("You must specify the same window size for steps 1 and 2."));
+      ::Effect::MessageBox(
+         XO("You must specify the same window size for steps 1 and 2.") );
       return false;
    }
    else if (mStatistics->mWindowTypes != mSettings->mWindowTypes) {
       // A warning only
-      ::Effect::MessageBox(_("Warning: window types are not the same as for profiling."));
+      ::Effect::MessageBox(
+         XO("Warning: window types are not the same as for profiling.") );
    }
 
    Worker worker(*mSettings, mStatistics->mRate
@@ -659,9 +665,12 @@ bool EffectNoiseReduction::Worker::Process
    for ( auto track : tracks.Selected< WaveTrack >() ) {
       if (track->GetRate() != mSampleRate) {
          if (mDoProfile)
-            effect.Effect::MessageBox(_("All noise profile data must have the same sample rate."));
+            effect.Effect::MessageBox(
+               XO("All noise profile data must have the same sample rate.") );
          else
-            effect.Effect::MessageBox(_("The sample rate of the noise profile must match that of the sound to be processed."));
+            effect.Effect::MessageBox(
+               XO(
+"The sample rate of the noise profile must match that of the sound to be processed.") );
          return false;
       }
 
@@ -684,7 +693,8 @@ bool EffectNoiseReduction::Worker::Process
 
    if (mDoProfile) {
       if (statistics.mTotalWindows == 0) {
-         effect.Effect::MessageBox(_("Selected noise profile is too short."));
+         effect.Effect::MessageBox(
+            XO("Selected noise profile is too short.") );
          return false;
       }
    }
diff --git a/src/effects/Paulstretch.cpp b/src/effects/Paulstretch.cpp
index f0b45f2dc..d57873071 100644
--- a/src/effects/Paulstretch.cpp
+++ b/src/effects/Paulstretch.cpp
@@ -256,7 +256,8 @@ size_t EffectPaulstretch::GetBufferSize(double rate)
 
 bool EffectPaulstretch::ProcessOne(WaveTrack *track,double t0,double t1,int count)
 {
-   auto badAllocMessage = _("Requested value exceeds memory capacity.");
+   const auto badAllocMessage =
+      XO("Requested value exceeds memory capacity.");
 
    const auto stretch_buf_size = GetBufferSize(track->GetRate());
    if (stretch_buf_size == 0) {
@@ -289,30 +290,35 @@ bool EffectPaulstretch::ProcessOne(WaveTrack *track,double t0,double t1,int coun
 
          /* i18n-hint: 'Time Resolution' is the name of a control in the Paulstretch effect.*/
          if ((minDuration / mProjectRate) < defaultPreviewLen) {
-            ::Effect::MessageBox (wxString::Format(_("Audio selection too short to preview.\n\n"
-                                               "Try increasing the audio selection to at least %.1f seconds,\n"
-                                               "or reducing the 'Time Resolution' to less than %.1f seconds."),
-                                             (minDuration / track->GetRate()) + 0.05, // round up to 1/10 s.
-                                             floor(maxTimeRes * 10.0) / 10.0),
-                            wxOK | wxICON_EXCLAMATION);
+            ::Effect::MessageBox(
+               XO("Audio selection too short to preview.\n\n"
+                  "Try increasing the audio selection to at least %.1f seconds,\n"
+                  "or reducing the 'Time Resolution' to less than %.1f seconds.")
+                  .Format(
+                     (minDuration / track->GetRate()) + 0.05, // round up to 1/10 s.
+                     floor(maxTimeRes * 10.0) / 10.0),
+               wxOK | wxICON_EXCLAMATION );
          }
          else {
             /* i18n-hint: 'Time Resolution' is the name of a control in the Paulstretch effect.*/
-            ::Effect::MessageBox (wxString::Format(_("Unable to Preview.\n\n"
-                                               "For the current audio selection, the maximum\n"
-                                               "'Time Resolution' is %.1f seconds."),
-                                             floor(maxTimeRes * 10.0) / 10.0),
-                            wxOK | wxICON_EXCLAMATION);
+            ::Effect::MessageBox(
+               XO("Unable to Preview.\n\n"
+                  "For the current audio selection, the maximum\n"
+                  "'Time Resolution' is %.1f seconds.")
+                  .Format( floor(maxTimeRes * 10.0) / 10.0 ),
+               wxOK | wxICON_EXCLAMATION );
          }
       }
       else {
          /* i18n-hint: 'Time Resolution' is the name of a control in the Paulstretch effect.*/
-         ::Effect::MessageBox (wxString::Format(_("The 'Time Resolution' is too long for the selection.\n\n"
-                                            "Try increasing the audio selection to at least %.1f seconds,\n"
-                                            "or reducing the 'Time Resolution' to less than %.1f seconds."),
-                                          (minDuration / track->GetRate()) + 0.05, // round up to 1/10 s.
-                                          floor(maxTimeRes * 10.0) / 10.0),
-                         wxOK | wxICON_EXCLAMATION);
+         ::Effect::MessageBox(
+            XO("The 'Time Resolution' is too long for the selection.\n\n"
+               "Try increasing the audio selection to at least %.1f seconds,\n"
+               "or reducing the 'Time Resolution' to less than %.1f seconds.")
+               .Format(
+                  (minDuration / track->GetRate()) + 0.05, // round up to 1/10 s.
+                  floor(maxTimeRes * 10.0) / 10.0),
+            wxOK | wxICON_EXCLAMATION );
       }
 
       return false;
diff --git a/src/effects/Repair.cpp b/src/effects/Repair.cpp
index afa2acbf3..0c3e92b47 100644
--- a/src/effects/Repair.cpp
+++ b/src/effects/Repair.cpp
@@ -88,7 +88,9 @@ bool EffectRepair::Process()
          const auto repair1 = track->TimeToLongSamples(repair_t1);
          const auto repairLen = repair1 - repair0;
          if (repairLen > 128) {
-            ::Effect::MessageBox(_("The Repair effect is intended to be used on very short sections of damaged audio (up to 128 samples).\n\nZoom in and select a tiny fraction of a second to repair."));
+            ::Effect::MessageBox(
+               XO(
+"The Repair effect is intended to be used on very short sections of damaged audio (up to 128 samples).\n\nZoom in and select a tiny fraction of a second to repair.") );
             bGoodResult = false;
             break;
          }
@@ -105,8 +107,10 @@ bool EffectRepair::Process()
          const auto len = s1 - s0;
 
          if (s0 == repair0 && s1 == repair1) {
-            ::Effect::MessageBox(_("Repair works by using audio data outside the selection region.\n\nPlease select a region that has audio touching at least one side of it.\n\nThe more surrounding audio, the better it performs."));
-   ///            The Repair effect needs some data to go on.\n\nPlease select an area to repair with some audio on at least one side (the more the better)."));
+            ::Effect::MessageBox(
+               XO(
+"Repair works by using audio data outside the selection region.\n\nPlease select a region that has audio touching at least one side of it.\n\nThe more surrounding audio, the better it performs.") );
+   ///            The Repair effect needs some data to go on.\n\nPlease select an area to repair with some audio on at least one side (the more the better).") );
             bGoodResult = false;
             break;
          }
diff --git a/src/effects/ScienFilter.cpp b/src/effects/ScienFilter.cpp
index d5357632d..3ab8d3dfc 100644
--- a/src/effects/ScienFilter.cpp
+++ b/src/effects/ScienFilter.cpp
@@ -348,7 +348,9 @@ bool EffectScienFilter::Init()
       {
          if (t->GetRate() != rate)
          {
-            Effect::MessageBox(_("To apply a filter, all selected tracks must have the same sample rate."));
+            Effect::MessageBox(
+               XO(
+"To apply a filter, all selected tracks must have the same sample rate.") );
             return false;
          }
       }
diff --git a/src/effects/TruncSilence.cpp b/src/effects/TruncSilence.cpp
index 37c662941..7502c50ca 100644
--- a/src/effects/TruncSilence.cpp
+++ b/src/effects/TruncSilence.cpp
@@ -343,7 +343,9 @@ bool EffectTruncSilence::ProcessIndependently()
                   - [&](const Track *pTrack){
                         return channels.contains(pTrack); };
             if (otherTracks) {
-               ::Effect::MessageBox(_("When truncating independently, there may only be one selected audio track in each Sync-Locked Track Group."));
+               ::Effect::MessageBox(
+                  XO(
+"When truncating independently, there may only be one selected audio track in each Sync-Locked Track Group.") );
                return false;
             }
          }
diff --git a/src/effects/nyquist/Nyquist.cpp b/src/effects/nyquist/Nyquist.cpp
index 1fbc5338b..266db8d91 100644
--- a/src/effects/nyquist/Nyquist.cpp
+++ b/src/effects/nyquist/Nyquist.cpp
@@ -560,10 +560,12 @@ bool NyquistEffect::Init()
       }
 
       if (!bAllowSpectralEditing || ((mF0 < 0.0) && (mF1 < 0.0))) {
-         Effect::MessageBox(_("To use 'Spectral effects', enable 'Spectral Selection'\n"
+         Effect::MessageBox(
+            XO("To use 'Spectral effects', enable 'Spectral Selection'\n"
                         "in the track Spectrogram settings and select the\n"
                         "frequency range for the effect to act on."),
-            wxOK | wxICON_EXCLAMATION | wxCENTRE, _("Error"));
+            wxOK | wxICON_EXCLAMATION | wxCENTRE,
+            XO("Error") );
 
          return false;
       }
@@ -775,8 +777,11 @@ bool NyquistEffect::Process()
 
    // Nyquist Prompt does not require a selection, but effects do.
    if (!bOnePassTool && (mNumSelectedChannels == 0)) {
-      wxString message = _("Audio selection required.");
-      Effect::MessageBox(message, wxOK | wxCENTRE | wxICON_EXCLAMATION, _("Nyquist Error"));
+      auto message = XO("Audio selection required.");
+      Effect::MessageBox(
+         message,
+         wxOK | wxCENTRE | wxICON_EXCLAMATION,
+         XO("Nyquist Error") );
    }
 
    Maybe<TrackIterRange<WaveTrack>> pRange;
@@ -808,8 +813,10 @@ bool NyquistEffect::Process()
 
                mCurTrack[1] = * ++ channels.first;
                if (mCurTrack[1]->GetRate() != mCurTrack[0]->GetRate()) {
-                  Effect::MessageBox(_("Sorry, cannot apply effect on stereo tracks where the tracks don't match."),
-                               wxOK | wxCENTRE);
+                  Effect::MessageBox(
+                     XO(
+"Sorry, cannot apply effect on stereo tracks where the tracks don't match."),
+                     wxOK | wxCENTRE );
                   success = false;
                   goto finish;
                }
@@ -827,11 +834,14 @@ bool NyquistEffect::Process()
 
             if (mCurLen > NYQ_MAX_LEN) {
                float hours = (float)NYQ_MAX_LEN / (44100 * 60 * 60);
-               const auto message = wxString::Format(
-                  _("Selection too long for Nyquist code.\nMaximum allowed selection is %ld samples\n(about %.1f hours at 44100 Hz sample rate)."),
-                  (long)NYQ_MAX_LEN, hours
-               );
-               Effect::MessageBox(message, wxOK | wxCENTRE, _("Nyquist Error"));
+               const auto message =
+                  XO(
+"Selection too long for Nyquist code.\nMaximum allowed selection is %ld samples\n(about %.1f hours at 44100 Hz sample rate).")
+                     .Format((long)NYQ_MAX_LEN, hours);
+               Effect::MessageBox(
+                  message,
+                  wxOK | wxCENTRE,
+                  XO("Nyquist Error") );
                if (!mProjectChanged)
                   em.SetSkipStateFlag(true);
                return false;
@@ -1385,9 +1395,12 @@ bool NyquistEffect::ProcessOne()
    }
 
    if (rval == nyx_string) {
-      wxString msg = NyquistToWxString(nyx_get_string());
+      // Assume the string has already been translated within the Lisp runtime
+      // if necessary, by gettext or ngettext defined below, before it is
+      // communicated back to C++
+      auto msg = Verbatim( NyquistToWxString(nyx_get_string()) );
       if (!msg.empty())  // Empty string may be used as a No-Op return value.
-         Effect::MessageBox(msg);
+         Effect::MessageBox( msg );
       else
          return true;
 
@@ -1399,18 +1412,16 @@ bool NyquistEffect::ProcessOne()
    }
 
    if (rval == nyx_double) {
-      wxString str;
-      str.Printf(_("Nyquist returned the value: %f"),
-                 nyx_get_double());
-      Effect::MessageBox(str);
+      auto str = XO("Nyquist returned the value: %f")
+         .Format(nyx_get_double());
+      Effect::MessageBox( str );
       return (GetType() != EffectTypeProcess || mIsPrompt);
    }
 
    if (rval == nyx_int) {
-      wxString str;
-      str.Printf(_("Nyquist returned the value: %d"),
-                 nyx_get_int());
-      Effect::MessageBox(str);
+      auto str = XO("Nyquist returned the value: %d")
+         .Format(nyx_get_int());
+      Effect::MessageBox( str );
       return (GetType() != EffectTypeProcess || mIsPrompt);
    }
 
@@ -1440,17 +1451,18 @@ bool NyquistEffect::ProcessOne()
 
    int outChannels = nyx_get_audio_num_channels();
    if (outChannels > (int)mCurNumChannels) {
-      Effect::MessageBox(_("Nyquist returned too many audio channels.\n"));
+      Effect::MessageBox( XO("Nyquist returned too many audio channels.\n") );
       return false;
    }
 
    if (outChannels == -1) {
-      Effect::MessageBox(_("Nyquist returned one audio channel as an array.\n"));
+      Effect::MessageBox(
+         XO("Nyquist returned one audio channel as an array.\n") );
       return false;
    }
 
    if (outChannels == 0) {
-      Effect::MessageBox(_("Nyquist returned an empty array.\n"));
+      Effect::MessageBox( XO("Nyquist returned an empty array.\n") );
       return false;
    }
 
@@ -1495,7 +1507,7 @@ bool NyquistEffect::ProcessOne()
       mOutputTime = outputTrack[i]->GetEndTime();
 
       if (mOutputTime <= 0) {
-         Effect::MessageBox(_("Nyquist returned nil audio.\n"));
+         Effect::MessageBox( XO("Nyquist returned nil audio.\n") );
          return false;
       }
    }
@@ -2054,7 +2066,10 @@ bool NyquistEffect::Parse(
                         tokens[3], mFileName.GetFullPath());
 
                // Too disturbing to show alert before Audacity frame is up.
-               //    Effect::MessageBox(str, wxT("Nyquist Warning"), wxOK | wxICON_EXCLAMATION);
+               //    Effect::MessageBox(
+               //       str,
+               //       wxOK | wxICON_EXCLAMATION,
+               //       XO("Nyquist Warning") );
 
                // Note that the AudacityApp's mLogger has not yet been created,
                // so this brings up an alert box, but after the Audacity frame is up.
@@ -2201,11 +2216,13 @@ bool NyquistEffect::ParseProgram(wxInputStream & stream)
    {
       /* i1n-hint: SAL and LISP are names for variant syntaxes for the
        Nyquist programming language.  Leave them, and 'return', untranslated. */
-      Effect::MessageBox(_("Your code looks like SAL syntax, but there is no \'return\' statement.\n\
+      Effect::MessageBox(
+         XO(
+"Your code looks like SAL syntax, but there is no \'return\' statement.\n\
 For SAL, use a return statement such as:\n\treturn *track* * 0.1\n\
 or for LISP, begin with an open parenthesis such as:\n\t(mult *track* 0.1)\n ."),
-                  Effect::DefaultMessageBoxStyle,
-                   _("Error in Nyquist code"));
+         Effect::DefaultMessageBoxStyle,
+         XO("Error in Nyquist code") );
       /* i18n-hint: refers to programming "languages" */
       mInitError = _("Could not determine language");
       return false;
@@ -2486,8 +2503,12 @@ bool NyquistEffect::TransferDataFromEffectWindow()
                   wxString token = tokenizer.GetNextToken();
                   if(!validatePath(token))
                   {
-                     const auto message = wxString::Format(_("\"%s\" is not a valid file path."), token);
-                     Effect::MessageBox(message, wxOK | wxICON_EXCLAMATION | wxCENTRE, _("Error"));
+                     const auto message =
+                        XO("\"%s\" is not a valid file path.").Format( token );
+                     Effect::MessageBox(
+                        message,
+                        wxOK | wxICON_EXCLAMATION | wxCENTRE,
+                        XO("Error") );
                      return false;
                   }
                }
@@ -2496,8 +2517,12 @@ bool NyquistEffect::TransferDataFromEffectWindow()
             else
             {
                /* i18n-hint: Warning that there is one quotation mark rather than a pair.*/
-               const auto message = wxString::Format(_("Mismatched quotes in\n%s"), ctrl->valStr);
-               Effect::MessageBox(message, wxOK | wxICON_EXCLAMATION | wxCENTRE, _("Error"));
+               const auto message =
+                  XO("Mismatched quotes in\n%s").Format( ctrl->valStr );
+               Effect::MessageBox(
+                  message,
+                  wxOK | wxICON_EXCLAMATION | wxCENTRE,
+                  XO("Error") );
                return false;
             }
          }
@@ -2508,8 +2533,12 @@ bool NyquistEffect::TransferDataFromEffectWindow()
          }
 
          // Validation failed
-         const auto message = wxString::Format(_("\"%s\" is not a valid file path."), ctrl->valStr);
-         Effect::MessageBox(message, wxOK | wxICON_EXCLAMATION | wxCENTRE, _("Error"));
+         const auto message =
+            XO("\"%s\" is not a valid file path.").Format( ctrl->valStr );
+         Effect::MessageBox(
+            message,
+            wxOK | wxICON_EXCLAMATION | wxCENTRE,
+            XO("Error") );
          return false;
       }
 
@@ -2781,8 +2810,9 @@ void NyquistEffect::OnLoad(wxCommandEvent & WXUNUSED(evt))
 {
    if (mCommandText->IsModified())
    {
-      if (Effect::MessageBox(_("Current program has been modified.\nDiscard changes?"),
-                       wxYES_NO) == wxNO)
+      if (wxNO == Effect::MessageBox(
+         XO("Current program has been modified.\nDiscard changes?"),
+         wxYES_NO ) )
       {
          return;
       }
@@ -2805,7 +2835,7 @@ void NyquistEffect::OnLoad(wxCommandEvent & WXUNUSED(evt))
 
    if (!mCommandText->LoadFile(mFileName.GetFullPath()))
    {
-      Effect::MessageBox(_("File could not be loaded"));
+      Effect::MessageBox( XO("File could not be loaded") );
    }
 }
 
@@ -2828,7 +2858,7 @@ void NyquistEffect::OnSave(wxCommandEvent & WXUNUSED(evt))
 
    if (!mCommandText->SaveFile(mFileName.GetFullPath()))
    {
-      Effect::MessageBox(_("File could not be saved"));
+      Effect::MessageBox( XO("File could not be saved") );
    }
 }
 
@@ -2882,9 +2912,12 @@ void NyquistEffect::OnTime(wxCommandEvent& evt)
    // so skip if value has not changed.
    if (val != value) {
       if (val < ctrl.low || val > ctrl.high) {
-         const auto message = wxString::Format(_("Value range:\n%s to %s"),
-                                               ToTimeFormat(ctrl.low), ToTimeFormat(ctrl.high));
-         Effect::MessageBox(message, wxOK | wxCENTRE, _("Value Error"));
+         const auto message = XO("Value range:\n%s to %s")
+            .Format( ToTimeFormat(ctrl.low), ToTimeFormat(ctrl.high) );
+         Effect::MessageBox(
+            message,
+            wxOK | wxCENTRE,
+            XO("Value Error") );
       }
 
       if (val < ctrl.low)
@@ -2923,9 +2956,11 @@ void NyquistEffect::OnFileButton(wxCommandEvent& evt)
       // Users should not normally see this, unless they are writing Nyquist plug-ins.
       if (wildcards % 2 != 0 || !validWildcards || ctrl.lowStr.EndsWith("|"))
       {
-         Effect::MessageBox(_("Invalid wildcard string in 'path' control.'\n"
-                        "Using empty string instead."),
-                        wxOK | wxICON_EXCLAMATION | wxCENTRE, _("Error"));
+         Effect::MessageBox(
+            XO("Invalid wildcard string in 'path' control.'\n"
+               "Using empty string instead."),
+            wxOK | wxICON_EXCLAMATION | wxCENTRE,
+            XO("Error") );
          ctrl.lowStr = "";
       }
    }
diff --git a/src/effects/vamp/VampEffect.cpp b/src/effects/vamp/VampEffect.cpp
index c9dc152c5..c53cb3163 100644
--- a/src/effects/vamp/VampEffect.cpp
+++ b/src/effects/vamp/VampEffect.cpp
@@ -313,7 +313,9 @@ bool VampEffect::Init()
          // So is this check not adequate?
           {
              // TODO: more-than-two-channels-message
-             Effect::MessageBox(_("Sorry, Vamp Plug-ins cannot be run on stereo tracks where the individual channels of the track do not match."));
+             Effect::MessageBox(
+                XO(
+"Sorry, Vamp Plug-ins cannot be run on stereo tracks where the individual channels of the track do not match.") );
              return false;
          }
       }
@@ -332,7 +334,7 @@ bool VampEffect::Init()
    mPlugin.reset(loader->loadPlugin(mKey, mRate, Vamp::HostExt::PluginLoader::ADAPT_ALL));
    if (!mPlugin)
    {
-      Effect::MessageBox(_("Sorry, failed to load Vamp Plug-in."));
+      Effect::MessageBox( XO("Sorry, failed to load Vamp Plug-in.") );
       return false;
    }
 
@@ -428,7 +430,8 @@ bool VampEffect::Process()
       {
          if (!mPlugin->initialise(channels, step, block))
          {
-            Effect::MessageBox(_("Sorry, Vamp Plug-in failed to initialize."));
+            Effect::MessageBox(
+               XO("Sorry, Vamp Plug-in failed to initialize.") );
             return false;
          }
       }