RPG Maker VX Ace

Allows you to store audio files in the encrypted archive

This script provides very simple audio encryption. It allows you to store audio files inside the rgss3a archive.
The data is decrypted and created outside of the archive when the game wants to play an audio file.

This means that while it is possible to easily copy the file once the game starts playing it, you can still protect files that they have not managed to unlock during the game.
Get it at Hime Works!