Dota 2 music packs
Music packs replace what plays in the menu and during a match, which is Valve's own kind of cosmetic and here it is free.
The D2PFX catalog has 19 mods in this category. Each changes what you see on your own screen; everyone else sees their own game.
Broodskoe
Rory in early 20s Music
Terraria Music
Magic Sticks of Dynamite
Northern Winds
The International 10
The International 2014
The International 2015
The International 2016
The International 2017
The International 2019
Dire Shred
deadmau5 dieback
Elemental Fury
Heroes Within
Humanity Last Breath
JJ Lin Timekeeper
TheFatRat Warrior
Sewerslvt Music
Installing any of these
Open Dota 2 Mod Manager, find the hero, press Install. The app puts the file in a free pak slot in the folder your game mounts, tells you when two mods carry the same file, and puts everything back after a Dota patch. The full guide, or the manual route if you would rather do it yourself.