its not tank music brother, the tank music is different, the climax is when big horde zombie come or you can said incoming attack

Yeah, well I tried it on The Ultimate Mod Testing and Reviewing Area (TUMTaRA) and it didn't play when I spawned the Tank in. I even unchecked my Tank music mods, and tried it. The default Tank theme played. I can only assume he meant it for the final rescue music once the evac arrives, but before you get in the rescue vehicle and end the level. (I hadn't tested my theory yet, but I may get around to it someday)

He means tank music

What do you mean Climax music? Is that supposed to be the music for when the rescue vehichle is ready, or what? Asking, because I've never heard the term used to describe something in-game.