In small sizes, horizontal lines and glyphs are not in the same vertical position
Submitted by Wilbert Berendsen
Assigned to poppler-bugs
As described in https://github.com/wbsoft/frescobaldi/issues/277 , sheet music (rendered by LilyPond) is not very well readable at small sizes, due to the fact that the horizontal lines are painted as single black lines and they are slightly offset w.r.t. glyphs that are positioned across these lines.
At larger sizes, the problem does not occur.
Programs using another poppler backend (such as Evince) do not suffer from this problem, which leads me to thinking it is an issue with the qt4 backend.