You can make a folder in SDK/Songs/ and fill it with different .wav files for custom songs you want in the game (I included a sample folder for test purposes). From there, you can make a data.ini file to configure the metadata for all the songs (check the PhantasyRow folder for an example of this). You will then be able to go to Scratch That and purchase these songs and listen to them on your in-game radio. However, this doesn't currently work with Xenia yet because apparently its powered by XBMP or something, I'm not entirely too sure.