First we will set up the main timeline. Open a new movie and insert 5 layers. They are from top to bottom:
1. Actions
2. Menu button
3. Menu bar mask
4. Sound movieclip
5. Menubar
Click-drag on frame 30 of the actions layer down to the menubar layer. This will select frame 30 on each layer. Right-click the black line and choose insert frame from the pop-up box.