In the end this was real tough for me to narrow down, but I thought that I would list out those that I would consider to be the top 5 movie Composers who did some truly great science fiction movie scores!
so here we got...
At number 5: David Arnold (Stargate).
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Now besides working on the sound track for the classic original, 'Stargate' movie, he has also worked on the music for such movies as, Quantum Of Solace (2008), Grindhouse (2007), and Independence Day (1996).
At number 4: Brad Fiedel (The Terminator).
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This guy has been a power house musician, having worked on both Horror and Science Fiction films as, Terminator 2: Judgement Day (1994), Fright Night (1985), Johnny Mnemonic (1995) to name a few!
At number 3: James Horner (Avatar).
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What can I say about this guy, he is pretty bad ass, I mean he scored some of Hollywood's most recently history making films, including: Titanic (1997) & Avatar (2009), so of course I had to include him in this list!
At number 2: Jerry Goldsmith (Star Trek: Nemesis).
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For me this guy is a true legend, I mean I love the work that this guy has done in both Science Fiction and Horror! Including such films as: Poltergeist (1982), The Omen (1976), Star Trek: The Motion Picture (1979) and Outland (1981) and that is to name just a few!
At number 1: John Williams (Raiders Of The Lost Ark).
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I know it sounds pretty cheesy and kind of the most obvious choice to pick for a science fiction movie composer, but some times the most obvious picks are the best, and in truth, in my opinion John Williams is by far the best most influential Science Fiction movie composer of all time, having composed some of the best music that has transcended time, such classic as the, 'Star Wars' score, the, 'Indiana Jones', score, the score for the first 2, 'Jaws' movies, 'Close Encounters Of the Third Kind', and that is a very small cross section of this guys prolific career!
Now there is a lot of other worthy composers out there that have done some truly amazing work on some truly amazing films, but in truth, these are the one's that I believe to be the best because they have helped compose music for some of the most influential Science Fiction films to come out of Hollywood!
http://youtu.be/A1OfX-0Q0tY
http://youtu.be/5WeO5ZxdCYM
http://youtu.be/xtVyu-A3vkY
http://youtu.be/s_F09jwNJtk
http://youtu.be/Jm8A9bHAaJs