I apologize. I believe I mis understood you in the past.
You have more than one category (example: Music, Videos) where each category has multiple reviews.
You would like the main page to display a list of all categories (such as Music, and Videos).
Is this correct?
That is what the "default" menu item already has built in. If you set the simple review menu item to default it will show you a list of categories to select from. The number of categories to display at once is a setting in the backend configuration. By default it will be 0 - which means display all.