A string quartet is a musical ensemble of four string players – two violin players, a viola player and a cellist – or a piece written to be performed by such a group. The string quartet is one of the most prominent chamber ensembles in classical music, with most major composers, from the mid to late 18th century onwards, writing string quartets.The string quartet was developed into its current form by the Austrian composer Joseph Haydn, with his works in the 1750s establishing the genre.