During their orchestration lessons, Harris introduced Davis to the TV composer Joe Harnell, who supported Davis during his search for work—his first job was working for composer Mark Snow's TV show Hart to Hart. He has worked as an orchestrator and conductor for Michael Kamen, Alan Silvestri, James Horner, Robert Folk, and Randy Newman.
Davis has been nominated seven times at the Primetime Emmy Awards, winning in 1995. He received a nomination for the Primetime Emmy Award for Outstanding Music Composition for a Series for Beauty and the Beast (1988), and for My Life and Times (1991). He received a nomination for Primetime Emmy Award for Outstanding Music Composition for a Limited or Anthology Series, Movie or Special (Original Dramatic Score) for Lies Before Kisses (1991), and A Little Piece of Heaven (1992), and House of Frankenstein (1998). He was twice nominated for the Primetime Emmy Award for Outstanding Music Composition for a Series in 1994 and 1995 for scores in SeaQuest DSV, winning in 1995.
He wrote scores mostly for television series up until 1995, in which he wrote a few of the cues for the animated Disney motion picture A Goofy Movie (1995). He continued to score television series until the two then young directors, the Wachowskis, hired him to score their neo-noir film Bound (1996). Davis has composed scores for films such as Universal Soldier: The Return (1999), Hulk (2003), House on Haunted Hill (1999), and Behind Enemy Lines (2001).
In 2004, he produced the music score for the BBC science fiction documentary series Space Odyssey: Voyage to the Planets, released as Voyage to the Planets and Beyond in the United States. Davis' magnum opus is the Matrix franchise: The Matrix (1999), The Matrix Reloaded (2003), The Matrix Revolutions (2004), and The Animatrix (2002). It was set apart from other film scores of its time for its atonality and avant garde style of composition, with influences from polytonal minimalist works by John Adams and cluster-like as well as aleatoric techniques prominent in the works of composer Witold Lutosławski.