The balanced, intimate sound of the string quartet (two violins, viola and cello) makes it irresistible to composers, and it became one of the cornerstones of the classical era, with Joseph Haydn often hailed as the “father” of the form. The string quartets of Beethoven, Mozart, Shostakovich and Bartók are considered among their most important works, employing an almost confessional inwardness and intensity.