Complex sentence: The organ removed in 1879 could be the "fine Walker organ" said to have come from Waltham Abbey and made "an absolutely splendid sound" which was installed at Little Clacton, Essex in 1939, and more recently sold on to Christ Church, Greenwich.
Split into simpler sentences: The organ removed in 1879 could be the "fine Walker organ" said to have come from Waltham Abbey and to have made "an absolutely splendid sound". This instrument was installed at Little Clacton, Essex in 1939, and later sold on to Christ Church, Greenwich.