Looking at the MisicTracks.qml file, I understand the folder to scan for music is set as follows:
Settings.setSetting("currentfolder", folderModel.homePath() + "/Music")
While this might work on the phone, it will fail on the desktop for anyone not using Ubuntu in English. The Music folder is part of the XDG translatable folders spec, so it will have a different name for each different locale.
As an example, I use Ubuntu in Catalan, so my music folder is called /home/dpm/Música, which is what the system created for me upon language selection during installation, and I haven't got a /home/dpm/Music folder.
I suspect on the phone, the path names of the user's folders will not be localized (as they're not visible on the phone), so I'll set the bug as wishlist for now.
We'll probably have to tackle this issue on the desktop when the app is convergent, but for now, we're tightly focused on phone.
Marking it as low for now, as the current focus is to get the app running on the phone, but we'll need to address this bug as part of the convergency story when running on the desktop (and when locales are properly supported on the phone)