I just tried, I'm on OFW (HAN enabled) so I can just install PKG. I had the official Muse songpack installed already, so I created a custom PKG DLC with the same numberas the Muse songpack that just includes the Peppa Pig song, and it doesn't appear on the list. However, I also tried with another conversion of a CDLC song, doing the same steps and it doesn't appear. I don't know if it's something wrong on my side or the CDLC just don't work.