     @IBAction func keyPressed(sender: UIButton) {
         let key = sender
         
+        // Turn off last key press in Mono
         if monoMode {
-            if let lastKey = lastKey where lastKey != key {
+            if let lastKey = lastKey {
                 turnOffKey(lastKey)
             }
         }
         
+        // Toggle key if in Hold mode
         if holdMode {
             if midiNotesHeld.contains(midiNoteFromTag(key.tag)) {
                 turnOffKey(key)

    func turnOffHeldKeys() {
        updateAllKeysToUpPosition()
        
        for note in midiNotesHeld {
            conductor.core.stopNote(note)
        }
    

        
        if holdMode && monoMode {
           toggleMonoKeyHeld(key)
           redisplayHeldKeys()
        } else if holdMode && !monoMode {
            toggleKeyHeld(key)
            
        } else {
            turnOffKey(key)
        }
    }
    
    // *********************************************************
