Question

Which section is not one of the four groups in the orchestral palette?



strings


voice


brass


percussion

Answer 1

recall, that orchestral general means instrumental. An orchestral piece, such as a symphony or a concerto, will always have strings, brass, and percussion

If you look at the first paragraph of the following article, you will get the basic definition of an orchestra:
https://en.wikipedia.org/wiki/Orchestra

After reading what I've told you, and looking at this article, the answer should be pretty clear. Hope this helped!