(sorry for the delay)
The audio-files come from https://www.audiotool.com, right?
Some of the files have a CC-BY-SA license, if you included music with that license you have to attribute them somewhere.
Putting it in the description/readme with a link to the source would suffice i think.
According to Audiotool's terms of service, each song belongs to their respective creator and as such is held to any license they choose... which probably means you need to ask each artist for permission individually.
Sorry for the late reply, would a lot of content need to be removed?
If it's just a few songs, go ahead and remove them, but if it's most of them... dunno, I don't feel like it would be too much of a problem due to the nature of the website, so I'll approve your package