Here is the classic string layout, with the addition of chorus parts above. Soloists or chorus are usually placed directly above the strings. When writing divisi for strings, it is usual to write the two parts on a single line (with stems up and down) unless the music is complex or there are multiple divisi, in which case separate staves. A solo instrument is written above the section, when both are playing together.
The Orchestra: A User's Manual is a free resource and will remain so. It still receives between 8,000 and 16,000 unique visits per month from all over the world. See the testimonials. Thanks to all the donations, I have been able to create this responsive re-design. But the movies and sound clips recorded in 2004 do show their age. I would really like to re-record everything and add many more techniques, especially for solo and ensemble writing. I estimate this will cost around £30,000. If you know a source of such funds, please contact me: a.hugill [at] bathspa.ac.uk