diff --git a/include/PianoRoll.h b/include/PianoRoll.h
index bc2a0d8cb..8f1dabdc3 100644
--- a/include/PianoRoll.h
+++ b/include/PianoRoll.h
@@ -295,7 +295,7 @@ private:
 
 	int m_oldNotesEditHeight;
 	int m_notesEditHeight;
-	int m_ppt;
+	int m_ppt;  // pixels per tact
 	int m_totalKeysToScroll;
 
 	// remember these values to use them