Heya! Sure, you can modify it however you want ^^
Viewing post in Pastel stripes Ren'py GUI comments
I assume you have problems with the fantasy gui? That's the one that had music. If it's searching for an audio file that isn't there then there's some reference left in the code for the original one. My guess is that you also removed the main menu music, but not the code referencing it? You can find that in options.rpy.