diff --git a/LEGO1/mxcompositemediapresenter.cpp b/LEGO1/mxcompositemediapresenter.cpp
index 01a6e135..454fb976 100644
--- a/LEGO1/mxcompositemediapresenter.cpp
+++ b/LEGO1/mxcompositemediapresenter.cpp
@@ -1,7 +1,12 @@
 #include "mxcompositemediapresenter.h"
 
 #include "legoomni.h"
+#include "legosoundmanager.h"
 #include "legovideomanager.h"
+#include "mxautolocker.h"
+#include "mxdsmultiaction.h"
+#include "mxobjectfactory.h"
+#include "mxtimer.h"
 
 DECOMP_SIZE_ASSERT(MxCompositeMediaPresenter, 0x50)
 
@@ -19,11 +24,65 @@ MxCompositeMediaPresenter::~MxCompositeMediaPresenter()
 	VideoManager()->RemovePresenter(*this);
 }
 
-// STUB: LEGO1 0x10074090
+// FUNCTION: LEGO1 0x10074090
 MxResult MxCompositeMediaPresenter::StartAction(MxStreamController* p_controller, MxDSAction* p_action)
 {
-	// TODO
-	return SUCCESS;
+	MxAutoLocker lock(&m_criticalSection);
+
+	MxResult result = FAILURE;
+	MxDSActionList* actions = ((MxDSMultiAction*) p_action)->GetActionList();
+	MxDSActionListCursor cursor(actions);
+	MxDSAction* action;
+
+	if (MxPresenter::StartAction(p_controller, p_action) == SUCCESS) {
+		// The usual cursor.Next() loop doesn't match here, even though
+		// the logic is the same. It does match when "deconstructed" into
+		// the following Head(), Current() and NextFragment() calls,
+		// but this seems unlikely to be the original code.
+		// The alpha debug build also uses Next().
+		// cursor.Head();
+		// while (cursor.Current(action)) {
+		// cursor.NextFragment();
+		while (cursor.Next(action)) {
+			MxBool success = FALSE;
+
+			action->CopyFlags(m_action->GetFlags());
+
+			const char* presenterName = PresenterNameDispatch(*action);
+			MxPresenter* presenter = (MxPresenter*) ObjectFactory()->Create(presenterName);
+
+			if (presenter && presenter->AddToManager() == SUCCESS) {
+				presenter->SetCompositePresenter(this);
+				if (presenter->StartAction(p_controller, action) == SUCCESS) {
+					presenter->SetTickleState(TickleState_Idle);
+
+					if (presenter->IsA("MxVideoPresenter"))
+						VideoManager()->RemovePresenter(*presenter);
+					else if (presenter->IsA("MxAudioPresenter"))
+						SoundManager()->RemovePresenter(*presenter);
+
+					success = TRUE;
+				}
+			}
+
+			if (success) {
+				action->SetOrigin(this);
+				m_list.push_back(presenter);
+			}
+			else if (presenter)
+				delete presenter;
+		}
+
+		if (!m_compositePresenter) {
+			SetTickleState(TickleState_Ready);
+			MxLong time = Timer()->GetTime();
+			m_action->SetUnknown90(time);
+		}
+
+		result = SUCCESS;
+	}
+
+	return result;
 }
 
 // STUB: LEGO1 0x100742e0
diff --git a/LEGO1/mxcompositemediapresenter.h b/LEGO1/mxcompositemediapresenter.h
index f28465f2..93a74642 100644
--- a/LEGO1/mxcompositemediapresenter.h
+++ b/LEGO1/mxcompositemediapresenter.h
@@ -27,7 +27,7 @@ public:
 
 	virtual void StartingTickle() override;                                           // vtable+0x1c
 	virtual MxResult StartAction(MxStreamController*, MxDSAction* p_action) override; // vtable+0x3c
-	virtual MxResult PutData();                                                       // vtable+0x4c
+	virtual MxResult PutData() override;                                              // vtable+0x4c
 
 private:
 	undefined2 m_unk0x4c; // 0x4c
diff --git a/LEGO1/mxcompositepresenter.h b/LEGO1/mxcompositepresenter.h
index 30dc170d..93148065 100644
--- a/LEGO1/mxcompositepresenter.h
+++ b/LEGO1/mxcompositepresenter.h
@@ -39,7 +39,7 @@ public:
 	virtual void VTable0x60(MxPresenter* p_presenter);                                             // vtable+0x60
 	virtual MxBool VTable0x64(undefined4 p_undefined);                                             // vtable+0x64
 
-private:
+protected:
 	MxCompositePresenterList m_list; // 0x40
 };