Music Typesetting. I've published a book and have been involved with a few related projects. I do pretty good work here. It pains me showing up to rehearsal and seeing poor quality sheet music on my stand. It's worse when these mistakes cause stoppage during rehearsals--usually easy mistakes that the person creating the end product could have fixed saving rehearsal time.
I have never been able to get things looking as nice as something like the Henle Urtext editions though, wonder what they use to put those together.