The narrower term "orchestration" is applied to the instrumentation of orchestral music. Since the most obvious differences of timbre are in those of various instruments, the art which blends and contrasts timbre is most easily discussed as the treatment of instruments; but we must use this term with philosophic breadth and allow it to include voices.
In Beethoven's orchestration there is almost always room for an independent viola part.
There is hardly one of Wagner's orchestral innovations which is not inseparably connected with his adaptation of music to the re q uirements of drama; and modern conductors, in treating Wagner's orchestration, as the normal standard by which all previous and contemporary music must be judged, are doing their best to found a tradition which in another fifty years will be exploded as thoroughly as the tradition of symphonic additional accompaniments is now exploded in the performances of Bach and Handel.
But the greatness of Wagner is shown in the fact that with all the effect his additions have in revolutionizing the resources of orchestration, he never regards his novelties as substitutes for the natural principles of instrumental effect.
At present we can only be certain that the criterion according to which Brahms, being a symphonic writer, has no mastery of orchestration whatever, is not a criterion compatible with any sense of symphonic style.