You can usually turn off Demonology’s lobby music by opening the settings and lowering the game’s music volume to zero. The game’s wiki also notes that lobby music can be changed in settings if you own the VIP Gamepass, and a forum answer says the only way to silence it is to mute music in the audio settings.

What to try

  1. Open the in-game menu.
  2. Go to Settings or Audio.
  3. Set Music Volume to 0.
  4. If that does not work, check whether the game has a separate lobby-music option tied to VIP Gamepass.

Important tradeoff

Turning music volume all the way down may also silence other music in the game, not just the lobby track. That is the most common limitation mentioned in Roblox music threads.

If it still plays

Some Roblox games control lobby audio with a special setting or gamepass feature rather than a full separate mute. In Demonology, the wiki specifically says the lobby music can be changed in settings only if you own VIP, which suggests non-VIP players may only have the full music mute option.

TL;DR

Set Music Volume to 0 in settings; if you have VIP, look for the lobby-music setting there too.