Simplify the following text for a Grade 6 native English-speaking person.
Original: The quartet was formed as the Moscow Conservatoire Quartet with Valentin Berlinsky on cello , Rostislav Dubinsky and Nina Barshai on first and second violins and Rudolf Barshai on viola , all members of a class taken by Mikhail Terian , the viola player of the Comitas Quartet .
Simplified: Rudolf Barshai was their viola player .