In the use of orchestral instruments, too, Mozart emulated the practice of the Mannheim composers. Their works were usually scored for eight parts, that is, two oboes _or_ flutes and two horns, besides the usual string body. Clarinets were still rare at that time, and parts provided for them were for that reason arranged for optional use, being interchangeable with the oboe parts. Mozart, although he had heard them as early as 1778 at Mannheim, used them only in his later works,[46] and even then did not often employ that part of their range which reaches below the oboe’s compass (still thinking of them as alternates for that instrument). But in the manner of writing for instruments Mozart’s works show a real novelty. In the Mannheim symphonies the wood wind instruments usually doubled the string parts, but occasionally they were given long, sustained notes and the brass even went beyond mere ‘accent notes’ (_di rinforza_) to the extent of an occasional sustained note or any individual motive. Haydn and Mozart at first confirmed this practice, but in their later works they introduced a wholly new method, which Dr. Riemann calls ‘filigree work’ and which formed the basis of Beethoven’s orchestral style. ‘The idea to conceive the orchestra as a multiplicity of units, each of which may, upon proper occasion, interpose an essential word, without, however, protruding itself in the manner of a solo and thus disturbing in any way the true character of the symphonic ensemble, was foreign to the older orchestral music.’[47] A mere dialogue between individual instruments or bodies of instruments was, of course, nothing new, but the cutting up of a single melodic thread and having different instruments take it up alternately, as Haydn did, was an innovation, and immediately led to another step, viz., the interweaving of individual melodic sections, dove-tail fashion, thus: [Illustration: Haydn: Finale, 36^{th} Symphony] and this in turn brought, with Mozart, the coöperation of _groups of instruments_ in such dove-tail formations, and led finally to the more sophisticated disposition of instrumental color, as in the second theme of the great G minor symphony: [Illustration: Music score] This sort of figure has nothing in common with the old polyphony, in which there is always one predominating theme, shifting from one voice to another. The equal and independent participation of several differently colored voices in the polyphonic web is the characteristic feature of modern orchestral polyphony, the style of Beethoven and his successors down to Strauss.