Complex sentence: He was an advisor to organ builders, such as for the organ of the Propsteikirche in Dortmund, built by Siegfried Sauer, and he played the opening concert on 23 October 1988.
Split into simpler sentences: He was an advisor to organ builders, such as for the organ of the Propsteikirche in Dortmund, built by Siegfried Sauer. He played the opening concert on 23 October 1988.