diff --git a/dlls/dmusic/dmusic_private.h b/dlls/dmusic/dmusic_private.h
index e7668a45281..1aa05364ce7 100644
--- a/dlls/dmusic/dmusic_private.h
+++ b/dlls/dmusic/dmusic_private.h
@@ -75,14 +75,14 @@ typedef struct DMUSIC_PRIVATE_CHANNEL_GROUP_ {
 /*****************************************************************************
  * ClassFactory
  */
-extern HRESULT WINAPI DMUSIC_CreateDirectMusicImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter);
-extern HRESULT WINAPI DMUSIC_CreateDirectMusicBufferImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter);
-extern HRESULT WINAPI DMUSIC_CreateDirectMusicDownloadedInstrumentImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter);
-extern HRESULT WINAPI DMUSIC_CreateDirectMusicDownloadImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter);
-extern HRESULT WINAPI DMUSIC_CreateReferenceClockImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter);
+extern HRESULT WINAPI DMUSIC_CreateDirectMusicImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter) DECLSPEC_HIDDEN;
+extern HRESULT WINAPI DMUSIC_CreateDirectMusicBufferImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter) DECLSPEC_HIDDEN;
+extern HRESULT WINAPI DMUSIC_CreateDirectMusicDownloadedInstrumentImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter) DECLSPEC_HIDDEN;
+extern HRESULT WINAPI DMUSIC_CreateDirectMusicDownloadImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter) DECLSPEC_HIDDEN;
+extern HRESULT WINAPI DMUSIC_CreateReferenceClockImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter) DECLSPEC_HIDDEN;
 
-extern HRESULT WINAPI DMUSIC_CreateDirectMusicCollectionImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter);
-extern HRESULT WINAPI DMUSIC_CreateDirectMusicInstrumentImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter);
+extern HRESULT WINAPI DMUSIC_CreateDirectMusicCollectionImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter) DECLSPEC_HIDDEN;
+extern HRESULT WINAPI DMUSIC_CreateDirectMusicInstrumentImpl (LPCGUID lpcGUID, LPVOID* ppobj, LPUNKNOWN pUnkOuter) DECLSPEC_HIDDEN;
 
 /*****************************************************************************
  * IDirectMusic8Impl implementation structure
@@ -151,10 +151,10 @@ struct IDirectMusicPortImpl {
   DMUSIC_PRIVATE_CHANNEL_GROUP group[1];
 };
 
-extern HRESULT WINAPI IDirectMusicPortImpl_Activate (LPDIRECTMUSICPORT iface, BOOL fActive);
+extern HRESULT WINAPI IDirectMusicPortImpl_Activate (LPDIRECTMUSICPORT iface, BOOL fActive) DECLSPEC_HIDDEN;
 
 /** Internal factory */
-extern HRESULT WINAPI DMUSIC_CreateDirectMusicPortImpl (LPCGUID lpcGUID, LPVOID *ppobj, LPUNKNOWN pUnkOuter, LPDMUS_PORTPARAMS pPortParams, LPDMUS_PORTCAPS pPortCaps);
+extern HRESULT WINAPI DMUSIC_CreateDirectMusicPortImpl (LPCGUID lpcGUID, LPVOID *ppobj, LPUNKNOWN pUnkOuter, LPDMUS_PORTPARAMS pPortParams, LPDMUS_PORTCAPS pPortCaps) DECLSPEC_HIDDEN;
 
 /*****************************************************************************
  * IReferenceClockImpl implementation structure
@@ -221,12 +221,12 @@ struct IDirectMusicInstrumentImpl {
 };
 
 /* custom :) */
-extern HRESULT WINAPI IDirectMusicInstrumentImpl_Custom_Load (LPDIRECTMUSICINSTRUMENT iface, LPSTREAM pStm);
+extern HRESULT WINAPI IDirectMusicInstrumentImpl_Custom_Load (LPDIRECTMUSICINSTRUMENT iface, LPSTREAM pStm) DECLSPEC_HIDDEN;
 
 /**********************************************************************
  * Dll lifetime tracking declaration for dmusic.dll
  */
-extern LONG DMUSIC_refCount;
+extern LONG DMUSIC_refCount DECLSPEC_HIDDEN;
 static inline void DMUSIC_LockModule(void) { InterlockedIncrement( &DMUSIC_refCount ); }
 static inline void DMUSIC_UnlockModule(void) { InterlockedDecrement( &DMUSIC_refCount ); }
 
@@ -266,17 +266,17 @@ typedef struct {
 #define GE(x) { &x, #x }
 
 /* dwPatch from MIDILOCALE */
-extern DWORD MIDILOCALE2Patch (const MIDILOCALE *pLocale);
+extern DWORD MIDILOCALE2Patch (const MIDILOCALE *pLocale) DECLSPEC_HIDDEN;
 /* MIDILOCALE from dwPatch */
-extern void Patch2MIDILOCALE (DWORD dwPatch, LPMIDILOCALE pLocale);
+extern void Patch2MIDILOCALE (DWORD dwPatch, LPMIDILOCALE pLocale) DECLSPEC_HIDDEN;
 
 /* check whether the given DWORD is even (return 0) or odd (return 1) */
-extern int even_or_odd (DWORD number);
+extern int even_or_odd (DWORD number) DECLSPEC_HIDDEN;
 /* FOURCC to string conversion for debug messages */
-extern const char *debugstr_fourcc (DWORD fourcc);
+extern const char *debugstr_fourcc (DWORD fourcc) DECLSPEC_HIDDEN;
 /* returns name of given GUID */
-extern const char *debugstr_dmguid (const GUID *id);
+extern const char *debugstr_dmguid (const GUID *id) DECLSPEC_HIDDEN;
 /* dump whole DMUS_OBJECTDESC struct */
-extern const char *debugstr_DMUS_OBJECTDESC (LPDMUS_OBJECTDESC pDesc);
+extern const char *debugstr_DMUS_OBJECTDESC (LPDMUS_OBJECTDESC pDesc) DECLSPEC_HIDDEN;
 
 #endif	/* __WINE_DMUSIC_PRIVATE_H */