What musical role does the viola play?

Answer 1

The viola is a member of the string family, sitting side-by-side with the violins, the cellos, and the string bass sections of the orchestra. Together they can play in infinite combinations depending on what the music requires.
In many orchestral pieces, the most important feature of the viola is that it is the "inner voice." It provides harmony and support for the violins, which are often in charge of the melody.
But this is not always the case. In several pieces, the violas have moments of great melodic importance, and can sometimes even steal the show. Composers such as Johannes Brahms even wrote works where the violas replaced the violins, for example in the orchestral "Serenade Number 2 in A, Op.16."
The violas work closely with the cellos and basses providing rhythmic support to the orchestra as well. The more pieces you listen to, the more aware you will become that every instrument can play many different roles in an orchestral work.

Answer 2

Usually harmony and accompaniment. They HATE being treated like 3rd violins.

Answer 3

Mainly the harmony.