In 2014, music kits were added to CS:GO. They let players customize the multiplayer shooter's soundtrack, because if you're going to reskin your guns why not reskin the main menu theme while you're at it? And if you win MVP in a match, why not make the other players listen to your MVP anthem?
The latest batch are called the Tacticians Music Kits, six new alternative soundtracks from various videogame composers. Notably, Austin Wintory—the award-winning composer of Journey, Abzû, and The Banner Saga, among others—is responsible for one that's a mash-up of polka and metal. Other contributors include Chipzel (Super Hexagon, Crypt of the Necrodancer), Freaky DNA (Retro City Rampage), Jesse Harlin (Mafia, various Star Wars games), Sarah Schachner (various Assassin's Creed games), and Laura Shigihara (Plants vs. Zombies, To the Moon, Rakuen).
Shigihara went the extra mile and animated a music video for her contribution in the style of an an0nymooose Source Filmmaker video, which is worth a watch if you want to see some serious military men throw a disco grenade and pose like J-pop idols.