Complex sentence: Admittedly though, Moore was slower in development when it came to purely orchestral works and most of his energy was directed towards opera, he wrote eight of them mostly on American subjects, though one notable exception is Giants in the Earth which concerns Norwegian immigrants.
Split into simpler sentences: Admittedly though, Moore was slower in development when it came to purely orchestral works and most of his energy was directed towards opera,. He wrote eight operas, mostly on American subjects, though one notable exception is Giants in the Earth which concerns Norwegian immigrants.