Why does moving audio files into a subfolder cause them to stop working?

In my project I'm referencing music files by name.

For some reason, if I move music files into subfolders in an attempt to organize them, they stop playing in-game.

To make things stranger, this only happens for most- rather than all music files.

My understanding is that folders are for organizing in the editor rather than for referencing, but despite that I'm able to reproduce the effect by moving music files in and out of subfolders.

Why does putting audio files in subfolders have this effect?

You need to specify the folder in with the sound name then. It probably says that in the manual. So if it’s in a folder called duck, the name would be “duck\quack.mp3”