prelim midi controller

src/ui/MainWindow.h

@@ -5,6 +5,7 @@
 #include <QKeyEvent>
 
 #include "../synth/AudioEngine.h"
+#include "../MidiController.h"
 
 QT_BEGIN_NAMESPACE
 namespace Ui { class MainWindow; }
@@ -30,5 +31,6 @@ private:
 
     AudioEngine* audio_ = nullptr;
     KeyboardController keyboard_;
+    MidiController midi_;
 
 };