Progressive rock artists wished to create music that was not limited to the structures of common popular rock and pop music. They wanted to make rock music that "progressed" to the complexity of jazz and classical music by creating a more serious, complex and sophisticated type of rock music. Progressive rock bands may have influences from psychedelic rock, folk music, traditional music, world music, and jazz or jazz fusion. It is also referred to as "prog rock" as an abbreviation, or as "Hobbit rock" because of frequent medieval or fantasy themes in the lyrics.