@MeltedPineapple hello! I suspect you're having an eXoDOS version of the game. @mitu is correct in saying there are parameters to help you configure your setup. To have the dosbox.conf (or any conf file or commands) you did use to launch the game would help a lot! Off top of my head here are some parameters you can use to run the game:c:\> monkey.exe r <- enable Roland MT-32 (requires specific files and setup) c:\> monkey.exe i <- enable internal speaker c:\> monkey.exe a <- enable Soundblaster and Adlib (most compatible) c:\> monkey.exe v <- force VGA
You can use a combination as well:c:\> monkey.exe a v <- enable Soundblaster and VGA
Search for Monkey Island reference card for DOS on the Web to get more keyboard shortcuts and interesting info. The most interesting shortcut for you would be Ctrl + S which turns on / off the sound (only working for Internal Speaker though).
Note: my recommendation would be for you to give a try to ScummVM for anything Lucasfilm games/LucasArts related. Very easy to use and you'll get the best experience possible. Check Retropie docs here for installation and ScummVM wiki to properly configure the games.