You must create at least one category for your products. We recommend a top level category with sub categories for Artists and Genres. Create additional categories for all your artists and use these as the "Main Category" for the products. You can assign products to other categories such as different genres.
The Genres give you another way to organize/show off your products. This could be other categories such as "Latest Releases" and "Award Winners". It is up to yu.
If you are a solo artist, just create a Category for yourself. You can use the same category in Products for "Artist" and "Main Category".
You can create menus that point to Categories or to a particular Category, which can list the products under that category in a blog or list format.
When you go to the main MyMuse admin menu, there will be an 'Options' icon at the top right. These are system wide options that set the default Category layout: a list of products as in rows of a table, or a columnar display with several products per row. These settings can be over ridden in the menu options.