The SimCity Theme is the music track that plays in the background on the 16-bit Windows version of SimCity (W16). The same song was also included in the upgraded SimCity Classic release. The song is a jazzy number composed by Russell Lieblich.
The SimCity Theme plays on a continuous loop right after the game boots up. It can be sent to any Windows-compatible MIDI device, but care must be taken to configure the MIDI setup correctly as the MIDI file houses both standard and extended versions of the instruments. There is a slight pause in the looping if you're using an MT-32, probably due to the driver resending the SysEx data.
The song's file name is SCWMUSIC.MID.
The upgraded SimCity Classic (W16) used the exact same music as the original, so it sounds identical.