In Luigi's Mansion 2 (3DS), the music files are compressed, meaning they are of lower quality than what they could be if uncompressed. Luigi's Mansion 2 HD (Switch) contains uncompressed versions of these music files, but it is currently unknown if they were from Luigi's Mansion Arcade.
Luigi's Mansion Arcade is an arcade game based on Luigi's Mansion 2 (3DS).
The image on the right is the arcade machine for Luigi's Mansion Arcade, used in Western regions.
One of the things Luigi's Mansion Arcade is known for toward modders is that it for some reason contains the uncompressed versions of every music file in Luigi's Mansion 2 (3DS). What's interesting is that most of it remains unused in the game's files.
With the gameplay footage provided by reviewers before the release of Luigi's Mansion 2 HD (Switch), most notably Nintendúo World, we can deduce that some of the sounds in the game remain compressed. The reason is likely because Nintendo didn't back up the original uncompressed sounds.