Why is SimCity 3000's music jazz?
Start with what is documented. The change from SimCity 2000, as the game's record states it, is the addition of a live music score, whose lead composer is Jerry Martin, incorporating new age and live jazz songs, with David Lauser on drums and Darol Anger on violin. The Windows credits fill in the shape of that decision: Martin is Sound and Music Director, the Compositions credit is shared by six people, Kirk Casey, Anna Karney, Robert Kauker, Kent Jolly, Jerry Martin and Marc Russo, and the Musicians credit names twenty players. This was a band and a department, not a lone composer at a keyboard.
Then consider who held the director's chair. Martin joined Maxis in 1996 as Studio Audio Director and Lead Composer, after a decade running his own company, Musicontrol, writing music for national television and radio commercials, over 200 commissions for clients including AT&T, Toyota, the NBA and Honda. He is described, plainly, as a composer best known for music particularly jazz, written for commercials. A studio that hands its city game to that man, and funds live players, gets the score SimCity 3000 has. That is the documented mechanism. Anything warmer, about jazz being the sound of cities, is a listener's reading, and it is labeled as such below.
The releases show the direction in physical form. Music From SimCity 3000, the 1999 Electronic Arts CD, runs ten tracks: every song composed by Jerry Martin, except "Concrete Jungle," composed by Martin and Marc Russo together. Discogs files the album under Electronic and Jazz, with styles listed as Future Jazz, Minimal and Ambient, which matches the game's split personality: half band, half synthesizer. A later fifteen track download release, given away free on the official site, spreads the composer credit across all six names from the game credits.
Reception kept the music at the front. IGN scored the game 9.0 and praised its sound among its strengths. A dedicated soundtrack review at ChoicestGames split the album into jazz and electronica, rated its artistic merit at 78 percent, and remembered a father walking in and asking, "Is that Miles Davis?" And a 2010 Destructoid community piece, one listener's account rather than a Maxis statement, credited this score with making its author fall in love with jazz, hearing in it a strong urban vibe. That urban reading is the popular answer to this page's question. It may even be right. But it comes from the audience, and the credits, the releases and the director's own career are the parts of the answer that can be proved.