I'm studying some classical compositions to see how to write properly for the string section. One thing I've noticed is that the Viola bar often has two notes playing at the same time whereas the Violin 1 & 2 often are playing single notes.
My confusion is mainly: how does one Viola section play two notes at the same time? Do they simply play the dyad on their instruments? Or does one half of the stands play the top and the other the bottom?
How does this translate to violins? I sometimes see separate Violin sections play dyad/octaves. In what cases is it acceptable to write these instead of just giving each section of the orchestra 'their own note'?