Jan Hammer (Czech pronunciation: [ˈjan ˈɦamɛr]) (born 17 April 1948) is a Czech-American musician, composer, and record producer. He first gained his most visible audience while playing keyboards with the Mahavishnu Orchestra during the early 1970s, as well as his film scores for television and film including "Miami Vice Theme" and "Crockett's Theme", from the 1980s television program Miami Vice. He has continued to work as both a musical performer and producer.

Hammer has collaborated with some of the era's most influential jazz and rock musicians such as John McLaughlin, Jeff Beck, Billy Cobham, Al Di Meola, Mick Jagger, Carlos Santana, Stanley Clarke, Tommy Bolin, Neal Schon, Steve Lukather, and Elvin Jones. He has composed and produced at least 14 original motion picture soundtracks, the music for 90 episodes of Miami Vice and 20 episodes of the television series Chancer.

JMJ himself and jarre-esque artists