Complex sentence: This artistic duo remained together for three years and gave in this period fully 120 concerts with changing programmes, studying a repertoire of 40 classical, romantic, contemporary and American-composed sonatas for violin and piano.
Split into simpler sentences: This artistic duo remained together for three years and gave in this period fully 120 concerts with changing programmes. The two musicians had by the end of it studied a repertoire of 40 classical, romantic, contemporary and American-composed sonatas for violin and piano.