going out on a limb here, since it is not really my area of expertise (do i even have an area of expertise?), but getting an entertainment visa from the little i know is not very difficult. a fair amount of women from south east asia come on that visa, plus most bands or solo artists that perform here in japan. however, again from the little i know, i think they r rather difficult to extend, so if u r thinking of something more permanent
i think u better look elsewhere. pls notice that i only think, not know.
for the entertainment visa u don't need a degree.
one option might be to get a specialist visa becoming a studio musician.
pls beware of that i have no idea whether or not that would be viable.
as always contact the japanese embassy/consulate in ur country or try the
immigration authority here in japan.