Complex sentence: On the day she arrives at his hut, she attempts to make the excuse that she can't play on it because it is out of tune, but is stunned to find that Baines has had the piano put into perfect tune.
Split into simpler sentences: On the day she arrives at his hut, she attempts to make an excuse that she can't play on the piano because it is out of tune. She is stunned to find that Baines has had the piano put into perfect tune.