diff --git a/src/AboutDialog.h b/src/AboutDialog.h
index 6f14a1844..be41fc65c 100644
--- a/src/AboutDialog.h
+++ b/src/AboutDialog.h
@@ -13,7 +13,6 @@
 
 #include "MemoryX.h"
 #include <vector>
-#include <wx/statbmp.h>
 #include <wx/bitmap.h>
 #include "widgets/wxPanelWrapper.h"
 
@@ -21,6 +20,8 @@ extern const wxString VerCheckArgs();
 extern const wxString VerCheckUrl();
 extern const wxString VerCheckHtml();
 
+class wxStaticBitmap;
+
 class ShuttleGui;
 
 struct AboutDialogCreditItem {
diff --git a/src/AdornedRulerPanel.h b/src/AdornedRulerPanel.h
index 6b0546aed..4e638376d 100644
--- a/src/AdornedRulerPanel.h
+++ b/src/AdornedRulerPanel.h
@@ -16,7 +16,6 @@
 
 #include "MemoryX.h"
 #include <wx/bitmap.h>
-#include <wx/dcmemory.h>
 
 class ViewInfo;
 class AudacityProject;
diff --git a/src/AudacityApp.h b/src/AudacityApp.h
index 7d1cd704c..53d998a5b 100644
--- a/src/AudacityApp.h
+++ b/src/AudacityApp.h
@@ -20,7 +20,7 @@
 #include "Experimental.h"
 
 #include "MemoryX.h"
-#include <wx/app.h>
+#include <wx/app.h> // to inherit
 #include <wx/cmdline.h>
 #include <wx/dir.h>
 #include <wx/docview.h>
diff --git a/src/AudacityException.h b/src/AudacityException.h
index 0c117a277..21552d309 100644
--- a/src/AudacityException.h
+++ b/src/AudacityException.h
@@ -17,7 +17,7 @@
  **********************************************************************/
 
 #include "MemoryX.h"
-#include <wx/app.h>
+#include <wx/app.h> // used in inline function template
 #include <exception>
 
 #include "Internat.h"
diff --git a/src/FFmpeg.cpp b/src/FFmpeg.cpp
index 843e0441e..1f11fa310 100644
--- a/src/FFmpeg.cpp
+++ b/src/FFmpeg.cpp
@@ -26,6 +26,7 @@ License: GPL v2.  See License.txt.
 #include "widgets/ErrorDialog.h"
 
 #include <wx/checkbox.h>
+#include <wx/dynlib.h>
 #include <wx/file.h>
 #include <wx/filedlg.h>
 
diff --git a/src/FFmpeg.h b/src/FFmpeg.h
index 5bc77f532..56d234fda 100644
--- a/src/FFmpeg.h
+++ b/src/FFmpeg.h
@@ -150,7 +150,6 @@ extern "C" {
 
 /* rather earlier than normal, but pulls in config*.h and other program stuff
  * we need for the next bit */
-#include <wx/dynlib.h>
 #include <wx/log.h>      // for wxLogNull
 #include <wx/utils.h>
 #include "widgets/LinkingHtmlWindow.h"
@@ -159,6 +158,8 @@ extern "C" {
 
 #include "audacity/Types.h"
 
+class wxDynamicLibrary;
+
 // if you needed them, any other audacity header files would go here
 
 /// Callback function to catch FFmpeg log messages.
diff --git a/src/FreqWindow.cpp b/src/FreqWindow.cpp
index 3a7190c1c..9307d50f3 100644
--- a/src/FreqWindow.cpp
+++ b/src/FreqWindow.cpp
@@ -57,6 +57,7 @@ and in the spectrogram spectral selection.
 #include <wx/file.h>
 #include <wx/filedlg.h>
 #include <wx/intl.h>
+#include <wx/scrolbar.h>
 #include <wx/sizer.h>
 #include <wx/slider.h>
 #include <wx/statbmp.h>
diff --git a/src/FreqWindow.h b/src/FreqWindow.h
index 714026260..3ecf5ebbf 100644
--- a/src/FreqWindow.h
+++ b/src/FreqWindow.h
@@ -14,18 +14,18 @@
 #include "MemoryX.h"
 #include <vector>
 #include <wx/brush.h>
-#include <wx/dcmemory.h>
 #include <wx/panel.h>
 #include <wx/dialog.h>
 #include <wx/gdicmn.h>
 #include <wx/pen.h>
 #include <wx/font.h> // member variable
-#include <wx/scrolbar.h>
 #include <wx/statusbr.h> // to inherit
 #include <wx/utils.h>
 #include "SampleFormat.h"
 #include "widgets/wxPanelWrapper.h"
 
+class wxMemoryDC;
+class wxScrollBar;
 class wxSlider;
 class wxTextCtrl;
 class wxButton;
diff --git a/src/HistoryWindow.cpp b/src/HistoryWindow.cpp
index e1d9576aa..d005787bb 100644
--- a/src/HistoryWindow.cpp
+++ b/src/HistoryWindow.cpp
@@ -28,6 +28,7 @@ undo memory so as to free up space.
 #include <wx/intl.h>
 #include <wx/listctrl.h>
 #include <wx/settings.h>
+#include <wx/spinctrl.h>
 #include <wx/stattext.h>
 #include <wx/textctrl.h>
 
diff --git a/src/HistoryWindow.h b/src/HistoryWindow.h
index f700ce77a..c20c9bbfd 100644
--- a/src/HistoryWindow.h
+++ b/src/HistoryWindow.h
@@ -12,11 +12,11 @@
 #define __AUDACITY_HISTORY_WINDOW__
 
 #include <wx/listctrl.h>
-#include <wx/spinctrl.h>
 
 #include "widgets/wxPanelWrapper.h"
 
 class wxButton;
+class wxSpinCtrl;
 class wxTextCtrl;
 class AudacityProject;
 class ShuttleGui;
diff --git a/src/LabelDialog.cpp b/src/LabelDialog.cpp
index d363ffc1f..02e1963bb 100644
--- a/src/LabelDialog.cpp
+++ b/src/LabelDialog.cpp
@@ -24,6 +24,7 @@
 #include <wx/filedlg.h>
 #include <wx/grid.h>
 #include <wx/intl.h>
+#include <wx/scrolbar.h>
 #include <wx/settings.h>
 #include <wx/sizer.h>
 #include <wx/stattext.h>
diff --git a/src/MixerBoard.h b/src/MixerBoard.h
index e4c895fb9..014a34603 100644
--- a/src/MixerBoard.h
+++ b/src/MixerBoard.h
@@ -18,7 +18,6 @@
 #include <wx/hashmap.h>
 #include <wx/image.h>
 #include <wx/scrolwin.h>
-#include <wx/statbmp.h>
 
 #include "widgets/ASlider.h"
 #include "widgets/wxPanelWrapper.h"
diff --git a/src/ModuleManager.h b/src/ModuleManager.h
index 30c742ae5..9c67f776e 100644
--- a/src/ModuleManager.h
+++ b/src/ModuleManager.h
@@ -12,8 +12,6 @@
 #ifndef __AUDACITY_MODULEMANAGER_H__
 #define __AUDACITY_MODULEMANAGER_H__
 
-#include <wx/dynlib.h>
-
 #include "MemoryX.h"
 #include <map>
 #include <vector>
@@ -21,6 +19,7 @@
 #include "audacity/ModuleInterface.h"
 
 class wxArrayString;
+class wxDynamicLibrary;
 class CommandHandler;
 
 wxWindow *  MakeHijackPanel();
diff --git a/src/ShuttleGui.h b/src/ShuttleGui.h
index 8826493d7..ab37cbe88 100644
--- a/src/ShuttleGui.h
+++ b/src/ShuttleGui.h
@@ -359,7 +359,8 @@ extern void SetIfCreated( wxStaticText *&Var, wxStaticText * Val );
 class GuiWaveTrack;
 class AttachableScrollBar;
 class ViewInfo;
-#include <wx/scrolbar.h>  // to get wxSB_HORIZONTAL
+
+#include <wx/defs.h>  // to get wxSB_HORIZONTAL
 
 // CreateStdButtonSizer defs...should probably move to widgets subdir
 enum
diff --git a/src/SplashDialog.h b/src/SplashDialog.h
index 5a87cec09..3cbb7201e 100644
--- a/src/SplashDialog.h
+++ b/src/SplashDialog.h
@@ -15,7 +15,6 @@
 #include <wx/dialog.h>
 #include "widgets/wxPanelWrapper.h"
 
-class wxStaticBitmap;
 class wxBitmap;
 class ShuttleGui;
 class AudacityProject;
diff --git a/src/Tags.cpp b/src/Tags.cpp
index fccee0db4..458a23975 100644
--- a/src/Tags.cpp
+++ b/src/Tags.cpp
@@ -60,6 +60,7 @@
 #include <wx/listctrl.h>
 #include <wx/notebook.h>
 #include <wx/radiobut.h>
+#include <wx/scrolbar.h>
 #include <wx/sizer.h>
 #include <wx/stattext.h>
 #include <wx/string.h>
diff --git a/src/TranslatableStringArray.h b/src/TranslatableStringArray.h
index 557683a1f..5ba428c4b 100644
--- a/src/TranslatableStringArray.h
+++ b/src/TranslatableStringArray.h
@@ -11,7 +11,7 @@ Paul Licameli
 #ifndef __AUDACITY_TRANSLATABLE_STRING_ARRAY__
 #define __AUDACITY_TRANSLATABLE_STRING_ARRAY__
 
-#include <wx/app.h>
+#include <wx/app.h> // used in inline function template
 
 class wxArrayStringEx;
 
diff --git a/src/commands/Command.h b/src/commands/Command.h
index f341f11e9..b1cfcfdcb 100644
--- a/src/commands/Command.h
+++ b/src/commands/Command.h
@@ -17,7 +17,6 @@
 #ifndef __COMMAND__
 #define __COMMAND__
 
-#include <wx/app.h>
 #include "../MemoryX.h"
 
 #include "CommandMisc.h"
diff --git a/src/effects/ChangePitch.cpp b/src/effects/ChangePitch.cpp
index 00898a101..5a3d745f6 100644
--- a/src/effects/ChangePitch.cpp
+++ b/src/effects/ChangePitch.cpp
@@ -31,6 +31,7 @@ the pitch without changing the tempo.
 #include <wx/choice.h>
 #include <wx/intl.h>
 #include <wx/slider.h>
+#include <wx/spinctrl.h>
 #include <wx/valtext.h>
 
 #include "../PitchName.h"
diff --git a/src/effects/ChangePitch.h b/src/effects/ChangePitch.h
index 3052c52fb..f37721fc1 100644
--- a/src/effects/ChangePitch.h
+++ b/src/effects/ChangePitch.h
@@ -25,14 +25,13 @@ the pitch without changing the tempo.
 #include "SBSMSEffect.h"
 #endif
 
-#include <wx/spinctrl.h>
-
 #include "SoundTouchEffect.h"
 
 class wxSlider;
 class wxChoice;
 class wxCheckBox;
 class wxTextCtrl;
+class wxSpinCtrl;
 class ShuttleGui;
 
 #define CHANGEPITCH_PLUGIN_SYMBOL ComponentInterfaceSymbol{ XO("Change Pitch") }
diff --git a/src/effects/Reverb.cpp b/src/effects/Reverb.cpp
index 1e1426445..4dbd3694e 100644
--- a/src/effects/Reverb.cpp
+++ b/src/effects/Reverb.cpp
@@ -21,6 +21,7 @@
 #include <wx/checkbox.h>
 #include <wx/intl.h>
 #include <wx/slider.h>
+#include <wx/spinctrl.h>
 
 #include "../Prefs.h"
 #include "../Shuttle.h"
diff --git a/src/effects/Reverb.h b/src/effects/Reverb.h
index e1f249774..da8ae586f 100644
--- a/src/effects/Reverb.h
+++ b/src/effects/Reverb.h
@@ -12,12 +12,11 @@
 #ifndef __AUDACITY_EFFECT_REVERB__
 #define __AUDACITY_EFFECT_REVERB__
 
-#include <wx/spinctrl.h>
-
 #include "Effect.h"
 
 class wxCheckBox;
 class wxSlider;
+class wxSpinCtrl;
 class ShuttleGui;
 
 #define REVERB_PLUGIN_SYMBOL ComponentInterfaceSymbol{ XO("Reverb") }
diff --git a/src/effects/ladspa/LadspaEffect.h b/src/effects/ladspa/LadspaEffect.h
index c7dfb7221..9643c0d09 100644
--- a/src/effects/ladspa/LadspaEffect.h
+++ b/src/effects/ladspa/LadspaEffect.h
@@ -15,7 +15,7 @@ class wxCheckBox;
 
 #include "../../MemoryX.h"
 #include <wx/dialog.h>
-#include <wx/dynlib.h>
+#include <wx/dynlib.h> // member variable
 
 #include "audacity/EffectInterface.h"
 #include "audacity/ModuleInterface.h"
diff --git a/src/toolbars/MixerToolBar.h b/src/toolbars/MixerToolBar.h
index d06942f25..5c8aa42f9 100644
--- a/src/toolbars/MixerToolBar.h
+++ b/src/toolbars/MixerToolBar.h
@@ -17,7 +17,6 @@
 class wxImage;
 class wxSize;
 class wxPoint;
-class wxStaticBitmap;
 
 class ASlider;
 
diff --git a/src/widgets/AttachableScrollBar.h b/src/widgets/AttachableScrollBar.h
index 1fcc03033..32e93e27f 100644
--- a/src/widgets/AttachableScrollBar.h
+++ b/src/widgets/AttachableScrollBar.h
@@ -17,7 +17,7 @@
 #ifndef __AUDACITY_ATTACHABLE_SCROLL_BAR__
 #define __AUDACITY_ATTACHABLE_SCROLL_BAR__
 
-#include <wx/scrolbar.h>
+#include <wx/scrolbar.h> // to inherit
 
 class ViewInfo;
 
diff --git a/src/widgets/BackedPanel.h b/src/widgets/BackedPanel.h
index e12937104..f945da6ca 100644
--- a/src/widgets/BackedPanel.h
+++ b/src/widgets/BackedPanel.h
@@ -10,7 +10,7 @@
 #define __AUDACITY_BACKED_PANEL__
 
 #include "../MemoryX.h"
-#include <wx/dcmemory.h>
+#include <wx/dcmemory.h> // member variable
 #include "wxPanelWrapper.h"
 
 
diff --git a/src/widgets/Grabber.h b/src/widgets/Grabber.h
index 2b00f922f..408624205 100644
--- a/src/widgets/Grabber.h
+++ b/src/widgets/Grabber.h
@@ -33,7 +33,7 @@ flicker-free use.
 
 #include <wx/defs.h>
 #include <wx/gdicmn.h>
-#include <wx/statbmp.h>
+#include <wx/statbmp.h> // to inherit
 
 ////////////////////////////////////////////////////////////
 /// Grabber Class