More general synonyms:
* Eclectic
* Versatile
* Multifaceted
* Diverse
* Varied
* Multifarious
Synonyms for specific contexts:
* Musical: Polystylistic, eclectic, cosmopolitan
* Literary: Multigenre, cross-genre, experimental
* Artistic: Polymorphic, eclectic, hybrid
Phrases:
* Drew inspiration from a wide range of sources
* Embraced a variety of styles
* Transcended genre boundaries
* Displayed mastery over multiple disciplines
The best synonym will depend on the specific context of your writing.