Grounds, Romberg & Boyd submitted a letter to the Opera House Committee to register for the International Competition for a National Opera House at Bennelong Point, Sydney, New South Wales, Australia on 11 January 1956, requesting the booklet with the competition brief - this became known as the “Brown book” (pdf).

A few weeks later, Roy Grounds wrote to Bob Newman of Bolt Beranek & Newman, an acoustic engineering firm based in Cambridge, Massachusetts. At this time, Grounds, Romberg & Boyd consults with this company on the acoustics for the Australian Academy of Science and the Sidney Myer Music Bowl concept designs. Grounds explains the Opera House project in brief and proposes working with the firm, suggesting that Robin Boyd will take “rough drafts” with him to MIT to discuss with them (pdf).

Two handwritten pages provide some sketches regarding general space planning and rough calculations for the seating angles and pitch of the auditoriums, as well as noting three books (“Stage Planning and Equipment For Multi-Purpose Halls” by P. Corry and “Theatre and Auditoriums” and “Scenery for the Theatre” by H. Burris-Meyer and E.C. Cole’) and two Architectural Review articles - one on the Civic Theatre in Malmö and the other on Corso Theatre in Zurich (pdf). Boyd had visited the Sigurd Lewerentz-designed Malmö theatre during his 1950 visit to Sweden.

There’s no further evidence in the archived files of Grounds, Romberg & Boyd of work on the Opera House competition - the firm must have abandoned the idea of submitting an entry at some point.