Leipzig Quartet plays masterfully but without subtlety

I first heard the Leipzig Quartet four years ago at the National Gallery. While generally praising it, I complained about insufficient clarity of articulation and wondered whether the cavernous acoustics were to blame. Well, they weren't. The group appeared Saturday in the more congenial Library of Congress auditorium, and the issue was the same: Fine as they are, the artists would be fully satisfying if they only employed a wider range of articulation, particularly sharper, drier bow-strokes.