The term "jazz rock" is sometimes used as a synonym for "jazz fusion" and for music performed by late 1960s and 1970s-era rock bands that added jazz elements to their music. After a decade of popularity during the 1970s, fusion expanded its improvisatory and experimental approaches through the 1980s in parallel with the development of a radio-friendly style called smooth jazz. Experimentation continued in the 1990s and 2000s. Fusion albums, even those that are made by the same group or artist, may include a variety of musical styles. Rather than being a codified musical style, fusion can be viewed as a musical tradition or approach.