Complex sentence: In 1876 he started working on "I mori di Valenza" (the project dates back to 1873), an opera he never finished, although it was completed later by Arturo Cadore and performed posthumously in 1914.
Split into simpler sentences: In 1876 he started working on "I mori di Valenza", although the project dates back to 1873. It was an opera that he never finished, although it was completed later by Arturo Cadore and performed posthumously in 1914.