A different mod than what I am used to do. Sonic Adventure DX was the game I played all the time growing up, even 100%ed the story mode. I distinctly remember how I used to do simple music swaps all the time, that was the best I could do at the time.
Which eventually lead to this.
Make sure this is loaded after the ADX Audio mod on the SADX Mod Manager. I also have a similar music swap for Sonic Adventure 2, but I need to make sure it's compatible with that game's Mod Manager.