diff --git a/TuneLab/Views/AutomationRenderer.cs b/TuneLab/Views/AutomationRenderer.cs
index 8facce0..8030a72 100644
--- a/TuneLab/Views/AutomationRenderer.cs
+++ b/TuneLab/Views/AutomationRenderer.cs
@@ -183,6 +183,16 @@ void Draw(string automationID)
             context.DrawCurve(points, Color.Parse(config.Color).Opacity(0.5), lineWidth);
         }
 
+        if (IsHover && ItemAt(MousePosition) is VibratoItem vibratoItem)
+        {
+            if (!vibratoItem.Vibrato.AffectedAutomations.ContainsKey(activeAutomation))
+            {
+                var vibrato = vibratoItem.Vibrato;
+                double x = TickAxis.Tick2X(vibrato.GlobalStartPos() + vibrato.Dur / 2);
+                context.DrawString("Drag to associate the vibrato.", new Point(x, 8), Brushes.White, 12, Alignment.CenterTop);
+            }
+        }
+
         lineWidth = 2;
         Draw(activeAutomation);
     }
diff --git a/TuneLab/Views/AutomationRendererItem.cs b/TuneLab/Views/AutomationRendererItem.cs
index 55cd904..b679753 100644
--- a/TuneLab/Views/AutomationRendererItem.cs
+++ b/TuneLab/Views/AutomationRendererItem.cs
@@ -17,7 +17,7 @@ class AutomationRenderItem(AutomationRenderer automationRenderer) : Item
 
     class VibratoItem(AutomationRenderer automationRenderer) : AutomationRenderItem(automationRenderer)
     {
-        public Vibrato Vibrato;
+        public required Vibrato Vibrato;
 
         public override bool Raycast(Point point)
         {
diff --git a/TuneLab/Views/AutomationRendererOperation.cs b/TuneLab/Views/AutomationRendererOperation.cs
index 779c162..13d023e 100644
--- a/TuneLab/Views/AutomationRendererOperation.cs
+++ b/TuneLab/Views/AutomationRendererOperation.cs
@@ -122,6 +122,8 @@ protected override void OnMouseRelativeMoveToView(MouseMoveEventArgs e)
                 }
                 break;
         }
+
+        InvalidateVisual();
     }
 
     protected override void OnMouseUp(MouseUpEventArgs e)
@@ -148,6 +150,16 @@ protected override void OnMouseUp(MouseUpEventArgs e)
             mMiddleDragOperation.Up();
     }
 
+    protected override void OnMouseEnter(MouseEnterEventArgs e)
+    {
+        InvalidateVisual();
+    }
+
+    protected override void OnMouseLeave()
+    {
+        InvalidateVisual();
+    }
+
     protected override void UpdateItems(IItemCollection items)
     {
         if (Part == null)
diff --git a/TuneLab/Views/PianoGrid.cs b/TuneLab/Views/PianoGrid.cs
index c635c27..105b827 100644
--- a/TuneLab/Views/PianoGrid.cs
+++ b/TuneLab/Views/PianoGrid.cs
@@ -490,6 +490,13 @@ void DrawVibratos(DrawingContext context)
         {
             var hoverVibrato = hoverVibratoItem.Vibrato;
 
+            var centerX = hoverVibratoItem.CenterX();
+            var pitch = hoverVibratoItem.Pitch();
+            if (double.IsNaN(pitch))
+            {
+                context.DrawString("Please draw pitch first in the area.", new Point(centerX, 32), textBrush, 12, Alignment.CenterTop);
+            }
+
             var frequencyPosition = hoverVibratoItem.FrequencyPosition();
             if (!double.IsNaN(frequencyPosition.Y))
             {
diff --git a/TuneLab/Views/PianoGridItem.cs b/TuneLab/Views/PianoGridItem.cs
index cd52440..789a0d8 100644
--- a/TuneLab/Views/PianoGridItem.cs
+++ b/TuneLab/Views/PianoGridItem.cs
@@ -119,12 +119,12 @@ public Point ReleasePosition()
             return new Point(PianoGrid.TickAxis.Tick2X(Vibrato.GlobalReleaseTick()), y);
         }
 
-        double CenterX()
+        public double CenterX()
         {
             return PianoGrid.TickAxis.Tick2X(Vibrato.GlobalStartPos() + Vibrato.Dur / 2);
         }
 
-        double Pitch()
+        public double Pitch()
         {
             return PianoGrid.Part == null ? double.NaN : PianoGrid.Part.Pitch.GetValue(Vibrato.Pos + Vibrato.Dur / 2) + 0.5;
         }