Check the songs in the SongsDLC File. Copy the columns (after year artist etc.) from one that is shown ingame, and paste them to your custom song.
Alternative: edit the name.txt with a other editor.
I have not made much with the vWii and don´t much inform about it. Would this work on the vWii or muss be make a special port made for it?
When yes, who would give up his time for this? :)
can´t add the link for it, search in google "solarus engine wii github"