This Google doc guide explains how to modify Sonic CD's music files for the purpose of speedrunning.

The link for it can be found here: https://docs.google.com/document/d/1NjxYE4YIUDer_IMxFW2j-8wf4mzlmh0poblwsR1AYB4/edit?usp=sharing

If you have any questions or concerns regarding this tutorial then feel free to let me know through DMs. I will update this guide every now and then when I feel the need to do so.