If anything, the string section is known for accumulating the longest amount of time of melodic material in symphonic pieces over the past five centuries. The reason for that is, first of all, most of the orchestra was made up of strings during most of that time frame, but also because string players have the capability to perform for long stretches of time. Unlike wind instruments, there is not as much muscle fatigue involved in the performance of the instrument, nor, of course, any breath issues. Therefore, strings was the go-to section when melodic, or any other kind of material, had to be distributed among the sections.
For the longest historical time this role was assigned to the first violins. We can find this with all kinds of composers throughout history, especially during the Baroque and Classic period, but also as late as the 20th century with composers like Mahler, Holst and Stravinsky: they all relied more on the first section of violins for placing their melodies, followed by the cello section, and very occasionally by the second violins and violas. It is also possible to find some melodies placed in the contrabass section, but very rarely without any other instrument doubling it.
It is also worth saying that it is very common to find one of the string sections –usually the first violins – opening the piece with the first melodic statement, passing it on then to other instrument or instrumental groups in the orchestra.
J. Haydn: Symphony 104, Hob. I:104, I movement
L. V. Beethoven: Symphony 6, Op. 68, I movement
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