A rock musical is a musical theatre work with rock music. The genre of rock musical may overlap somewhat with album musicals, concept albums and song cycles, as they sometimes tell a story through the rock music, and some album musicals and concept albums become rock musicals. Notable examples of rock musicals include Hair, Grease, Rent, Spring Awakening, and Next to Normal. The Who's Tommy and other so-called rock operas are sometimes presented on stage as a musical.