See attached, which translates to :
[Media Type]=[Audio] [Last Played]=>30d ([Genre]=[Jazz],[Big Band//Vocalists] or ([Genre]=[Classical] [Rating]=5)) ~sort=Random
The UI for entering AND or OR grouping needs some love. Aside from being invisible, it is often difficult to enter complex expressions as MC keeps removing the grouping and the grouping is often required to select from fields that have been previously narrowed by earlier rules. But, they get removed when you add a new rule, so you have to keep adding them. Use the Import/Export area when possible.