I'm sure you got this figured out by now, but if not, I worked out a simple solution:
<?php show_menu2(0, 89, SM2_ALL, SM2_ALL,'<li><span class="menu-default">[ac][menu_title]</a></span>','</li>','<ul>','</ul>');?>
The trick is, 89 is the id of an unused "hidden" (dummy) root parent page of "CDs". This way the child page "CDs" is shown, and then all children of the CDs page are shown as well.
Hope this helps.