music/audiosearch -> search/audio | How to keep submenu open (menustructure)

Hello

I hope somebody can help me. I was not sure where to post this and put it into the post installation forum but nobody could help me so maybe here somebody can. :-)

I'm still struggling with the menu and structuring with Drupal.
I'm building a new menu, which allows the visitor of my site to access content and functions trough an organized menu.
Therefor I'm building a menu system based on URLs to reflect a 2 level menu hierarchy.

So now I have a menu item "music" and a submenu item "audiosearch". Clicking on audiosearch shall open the search form for audio. This function can be access trough the URL search/audio. Therefore I tried to map music/audiosearch to search/audio . I was trying to do it by creating a new menu item in the admin menu, putting it in the right place and filling in the URL search/audio. I also tried to use goto_drupal() in a module which I use to define the main menu.

The problem is that both ways the correct page is opened but as the URL changes the submenu with the just clicked menu item "audiosearch" disappears and the parent item "music" isn't highlighted either.

What shall I do to solve this problem?