Complex sentence: The theatre was acquired by the Dunedin Opera Company in 1967 which converted it to a live venue, reducing the seating capacity from 862 to 413 by removing the ground floor stalls and advancing the proscenium into the auditorium to achieve a greater stage depth.
Split into simpler sentences: The theatre was acquired by the Dunedin Opera Company in 1967 which converted it to a live venue. The seating capacity was reduced from 862 to 413 by removing the ground floor stalls and advancing the proscenium into the auditorium to achieve a greater stage depth.