You can edit MIDI on the weakest of computers. It takes no RAM (or very little, yours is more than enough) and no fast processor. An Atari from the eighties is just as good as today's fastest computer for just MIDI (in fact, my old Mega 1040ST had better MIDI timing than any current system)...

I'm a Mac user, so no recommendations, here. But I'm sure some of the SZ community on the Dark Side of the Force can make a recommendation or two...