Conversation so far:
What instruments do they play in an orchestra?
four groups of related musical instruments called the woodwinds, brass, percussion, and strings.
Are any other instruments played along with an orchestra?
piano and celesta may sometimes be grouped into a fifth section such as a keyboard section or may stand alone.
Are there different types of orchestras?
Chamber orchestra usually refers to smaller-sized ensembles.
Is there another type of orchestra?
A symphony orchestra will usually have over eighty musicians on its roster, in some cases over a hundred.
Are there any other types of orchestras?
The terms symphony orchestra and philharmonic orchestra may be used to distinguish different ensembles from the same locality.
How big are most orchestras?
CANNOTANSWER.
Was there any more interesting information?
In the 20th century, new repertory demands expanded the instrumentation of the orchestra.
What happened because of the expanded instrumentation?
a flexible use of the classical-model instruments and newly developed electric and electronic instruments in various combinations.
Is there an orchestra that is most popular?
CANNOTANSWER.

Question: How many people are usually in an orchestra?
Self-contained rewrite: How many musicans play in an orchestra?