This is the Main Menu OST music fr om Digital Integration iF-16 Fighting Falcon flight sim fr om the 90's.
Not trying to undermine the great work from Eagle Dynamics artists, but being a 90's flight simulator enthusiast, I've spend countless of hours playing that sim in my junior years. Adding the main menu theme in DCS somewhat pays the least tribute to an awesome 90's classic simulator.
Just copy and paste the Mods folder into your main DCS World directory and replace wh ere necessary.