TTT middle round random music by Geferon

This download looks like an addon. You need to extract the downloaded zip and put the addon folder in your Garry's Mod addons folder. You should end up with a directory structure similar to below:

• steamapps
  • common
    • garrysmod
      • garrysmod
        • addons
          • randommusic <-- Addon folder!
            • e.g.
            • lua
            • maps
            • materials
            • models
            • etc

• randommusic/
  • lua/
    • autorun/
      • client/
        • cl_randommusic.lua
      • music_config.lua
      • server/
        • sv_randommusic.lua

Pastelnk, perec_v_glaza, Lala San, WingNutNT, Francisco Rodrigues, [MG] Bürogebäude, 【新城龍一】-longの舞-, 【新城龍一】-longの舞-, Zinx, ZERTON SPACE™, SiR Bluquer, Evelin, Evelin, Matixto | TGX.es, Isaac Asimov, jhared117, Alpha, QSAU | Sassy, Jaszczur Z Kosmosu @Liveserver, Red, Red, Tandul, NOWAYS., NOWAYS., NOWAYS., cheetahx7x hellcase.com, starcrash9, FlaserHD, [HDK]Blacky, Noctis Lucis Caelum, ViperSRT, Zoldyck, Mrkevinhyt24, SIGZZANG, scuZy, Levatos, stupidforce, Bryan, Hody, TheSoulrester, Herr_Blitz, Keepo, quh419, The Law, Enot21, Papabear, Stoned Coal, #FreDyi FanBoy <3 ;), Beast, albanerletsplay1 +73 others