Complex sentence: The musicians were replaced in 1843 by an organ, the present organ was installed in 1973, it was built by Laycock and Bannister and was bought second hand from a church in Middlesbrough that was closing.
Split into simpler sentences: The musicians were replaced in 1843 by an organ. It was built by Laycock and Bannister and was bought second hand from a church in Middlesbrough that was closing.