Complex sentence: It is famous for its association with composer Healey Willan who was organist and choir-master for well over four decades; it was part of the composite Robertson Davies used to form St. Aidan's "in his novel" The Cunning Man.
Split into simpler sentences: It is famous for its association with composer Healey Willan who was organist and choir-master for well over four decades. SMM was part of the composite Robertson Davies used to form St. Aidan's "in his novel" The Cunning Man.