In the last mvt. of Tchaikovsky's 6th there is a passage where the
>melody is composed of notes alternating between the firsts and
>seconds, an effect expressive of restlessness and anxiety--and
>completely effaced if the violin sections are not separated.
I love this passage in Tchaikovsky - it's something he does fairly often where the ear hears a melody (or motif) which no-one in the orchestra actually plays. I don't think it's an accident.
All the best,
Lawrence
http://lawrenceyates.co.uk