(written from a Production point of view)
James Thatcher is a musician, specialized in playing the French Horn, who worked for Dennis McCarthy, Ron Jones, and Jerry Goldsmith on episodes of Star Trek: The Next Generation and two Star Trek films.
Thatcher has been the lead French horn player for composers such as John Williams, James Newton Howard, James Horner, Steve Jablonsky, Hans Zimmer, Brian Tyler, and Alan Silvestri. His brother George Thatcher is also a musician, performing the bass trombone on several film soundtracks  and his sister Jan Chamberlin is a singer and vocal coach. 
Thatcher himself has started his career at the age of 16, performing and studying with his uncle George Thatcher, former principal hornist with the National Symphony of Mexico. He has been a member of the Phoenix Symphony, the Utah Symphony, the Pacific Symphony and the Los Angeles Philharmonic and is currently principal horn of the Pasadena Symphony, the New West Symphony and the Los Angeles Music Center Opera.
He received the Most Valuable Player Award from the National Association of Recording Arts and Sciences as the most often heard horn player in the world, performing in 70 to 80 film scores in the last 27 years. Thatcher is also co-professor of horn at the USC Thornton School of Musics located in Los Angeles, California.
Among his over 1,000 film scores are the science fiction films The Black Hole (1979) and E.T. the Extra-Terrestrial (1982), the music drama Flashdance (1983), the science fiction comedy Back to the Future (1985), the Academy Award winning drama The Color Purple (1985), the television series Airwolf (1984-1986), the fantasy horror film The Witches of Eastwick (1987), the drama Good Morning, Vietnam (1987), the action thriller Die Hard (1988), Michael Jackson's Moonwalker (1988), the drama Dead Poets Society (1989), Disney's The Little Mermaid (1989), the romance Pretty Woman (1990), the Academy Award winning films Dick Tracy and Dancing with Wolves (both 1990), the fantasy films The Addams Family and Hook (both 1991), the action thriller Under Siege (1992), the music drama The Bodyguard (1992), Steven Spielberg's Jurassic Park and Schindler's List (both 1993), Disney's The Lion King (1994) and Toy Story (1995), the science fiction film Independence Day (1996), the science fiction comedy Mars Attacks! (1996), James Cameron's Titanic (1997), the sci-fi thriller Starship Troopers (1997), the fantasy film The Mummy (1999), Ridley Scott's Gladiator (2000), the drama Pearl Harbor (2001), the drama A Beautiful Mind (2001), Ice Age (2002), the reboot Batman Begins (2005), the sequels X-Men: The Last Stand (2006), The Fast and the Furious: Tokyo Drift (2006, directed by Justin Lin), and Pirates of the Caribbean: At World's End (2007), James Cameron's science fiction adventure Avatar (2009, starring Zoe Saldana), the sequels Fast Five and Pirates of the Caribbean: On Stranger Tides (both 2011), the comic adaptations X-Men: First Class (2011) and Green Lantern (2011), and the science fiction reboot Rise of the Planet of the Apes (2011).
More recently, Thatcher played the French horn on the reboot The Amazing Spider-Man (2012), the animated comedy Frozen (2013), and the comedy sequel Ted 2 (2015).