I am arranging a piece of music, and I am having trouble figuring out how to notate a double stop with the notes G and G#. The key is G, and it's for mallet percussion. The notes are repeated once. The software I'm using (MuseScore) does it as in the picture below, but that looks really weird to me. Is it correct? If not, what is the correct way to notate it?
There's also a curious but non-ambiguous way to do it: using a sort of a "secondary stem" like this:
(here the fourth chord contains both a B♭ and a B on the "secondary stem"). The only problem is that Musescore probably won't be able to render that. In that case, I would recommend writing G and A♭, as pointed out in the other answers.