Liv Maessen is an Australian pop singer who gained prominence in the late 1960s and early 70s. Her musical style is characterized by a melodic pop sound, and she is best known for her Top 10 hit "Knock, Knock Who's There?" which made her the first Australian female solo artist to sell over one million copies in the international market. Despite her brief career, Maessen's success left a lasting impact on the Australian music industry, paving the way for future female solo artists.