Yet during the period of orchestral development under Haydn and Mozart the strings remained the solid basis for orchestral writing, partly because of their greater practical efficiency, and partly because the reserved character of the violin tone appealed more to the classic sense of moderation. And even with the increased importance of the wood-winds the unit of writing was the group and not the individual instrument (barring occasional special solos). The later history of orchestral writing was one of a gradually increasing importance and independence for the wood-wind section (and later for the brass) and of individualization for each separate instrument. Mozart based his writing upon the Mannheim orchestration and upon Haydn, showing considerable sensitiveness to timbres, especially that of the clarinet. Haydn, in turn, learned from Mozart’s symphonies, and in his later works for the orchestra further developed freedom of writing, being particularly fond of the oboe. Beethoven emancipated all the instruments, making his orchestra a collection of individual voices rather than of groups (though he was necessarily hampered by the technically clumsy brass). Yet, compared to the writing of Berlioz and Liszt, the classical symphonies were in their orchestration rather dry and monochrome (always making a reservation for the pronounced romantic vein in Beethoven). Haydn and Mozart felt orchestral contrasts, but they used them rather for the sake of variety than for their absolute expressive value. So that, however these composers may have anticipated and prepared the way for the romanticists, the difference between the two orchestral palettes is striking. One might say it was the difference between Raphael’s palette and Rubens’. And in mere externals the romanticists worked on a much larger scale. The string orchestra in Mozart’s time numbered from twenty-two to thirty instruments, and to this were added usually two flutes and two horns, and occasionally clarinets, bassoons, trumpets, and kettle-drums in pairs. Beethoven’s orchestra was little larger than this, and the capabilities of his instruments only slightly greater, but his use of the various instruments as peculiar and individual voices was masterly. All the great composers of the second quarter of the nineteenth century studied his instrumentation and learned from it. But Beethoven, though he sought out the individual character of orchestral voices, did not make them sensuously expressive as Weber and Liszt did. About the time of Beethoven’s death the use of valves made the brass possible as an independent choir, capable of performing most of the ordinary diatonic and accidental notes and of carrying full harmony. But it must be said that even the most radical of the romantic composers, such as Berlioz, did not avail themselves of these improvements as rapidly as they might, and were characteristic rather in their way of thinking for instruments than in their way of writing for them.