Messages and commands are nearly identical: they both have a name,

they can both have parameters stashed in a table, and they both play
stuff out of the actor command list.  Merge them; now the only
difference between playing and broadcasting a command is that playing
plays recursively on a tree and broadcasting sends to all subscribers.

The distinction between "messages" and "commands" is cosmetic now;
everything is a message.  The only thing special about commands intended
to be received as a broadcast is the "Message" suffix, which subscribes it.

stepmania/src/Transition.cpp

@@ -66,12 +66,12 @@ bool Transition::EarlyAbortDraw() const
 /* Our parent might send us OnCommand.  We do that ourself, because
  * we sometimes want to know GetLengthSeconds before StartTransitioning.
  * Make sure we don't process OnCommand twice. */
-void Transition::PlayCommand( const RString &sCommandName, const LuaReference *pParamTable )
+void Transition::HandleMessage( const Message &msg )
 {
-	if( sCommandName == "On" )
+	if( msg.GetName() == "On" )
 		return;
 
-	ActorFrame::PlayCommand( sCommandName, pParamTable );
+	ActorFrame::HandleMessage( msg );
 }
 
 void Transition::StartTransitioning( ScreenMessage send_when_done )