Team Fortress 2 Classic Main Theme
"Team Fortress 2 Classic Main Theme" is a song remixed from "Ecce gratum," a reference to the opening video of the original Team Fortress mod. The remix was written by 
MrModez and released as part of the Team Fortress 2 Classic soundtrack. The remix adds a layer of "TF2-styled" percussions and the TF2 main theme's iconic orchestra hit at the end.
It is 58 seconds long and can be heard on the game's main menu. This song can also be heard in the "2.0.4 Release Announcement" video.