Specialising in the German repertory, she went on to sing Wagner's Elsa, Sieglinde, Gutrune, Senta and Isolde, but her greatest success at Covent Garden was undoubtedly the Marschallin in Der Rosenkavalier, a role which suited her vocally, dramatically and temperamentally. Another very sympathetic part was Ellen Orford in Peter Grimes, and after leaving Covent Garden in 1964, she sang many of the other roles in Britten operas created by Joan Cross, and herself created one, Miss Wingrave, in Britten's television opera, Owen Wingrave.
Sylvia Fisher was born in Melbourne, and studied there at the Albert Street Conservatorium with Mary Campbell. While a student she sang Hermione in Lully's Cadmus et Hermione at the Comedy Theatre, her only stage appearance until her arrival in Britain. After winning the Melbourne Sun Aria Contest, in which she sang "Elisabeth's Greeting" from Tannhauser, she embarked on a career as a concert singer, while studying further with Adolf Spivakowsky, to whom she attributed her later success.
A regular broadcaster with the Australian Broadcasting Commission, she sang much oratorio - Bach's Mass in B Minor, Handel's Messiah and Israel in Egypt, Beethoven's Missa Solemnis and Ninth Symphony, Brahms' German Requiem and the Verdi Requiem - but she also sang several operatic roles (Donna Anna in Don Giovanni, Ortrud in Lohengrin and Aida) and gave many lieder recitals.
After the Second World War she decided to go to London, booking a passage in October 1947. Although she carried a letter of introduction to Sir David Webster, the general administrator of the Covent Garden Opera Company, it was not until a year after her arrival - and after five auditions - that she was engaged, making her debut on 9 December 1948 in Fidelio. When the German director Friedrich Schramm heard that she had never appeared on any stage before he said: "Good! All you need to do is to leave your hands at your sides and sing. Let the music speak for itself."
This excellent advice she followed for the rest of her career. Though by now a trifle mature to look convincing as a boy, Sylvia Fisher scored a considerable success as Leonore / Fidelio. Her warm-toned, resonant voice was greatly admired, as was her excellent diction (Fidelio, like most of the Covent Garden repertory at that time, was sung in English) and the dignity of her stage bearing. Her other roles during the 1948/49 season were Countess Almaviva in The Marriage of Figaro and Third Norn in Gotterdammerung.
The following season , by now an established and popular member of the company, Fisher took on three new roles, two of them destined to be among her finest. Her first Marschallin, though only a sketch of the superb portrayal that she was later to achieve, was none the less interesting.
A gentle, radiantly sung Elsa in Lohengrin was followed by Sieglinde in Die Walkure, another characterisation that was to develop with the years until it became a performance worthy to compare with that of the great Lotte Lehmann.
The 1950/51 season opened with The Flying Dutchman, but Senta was never one of her more congenial Wagner roles; her Gutrune in Gotterdammerung, though, was more successful.
That season Sylvia Fisher sang in Der Rosenkavalier again, now conducted by Erich Kleiber, and immediately it became clear that a transformation had taken place. Gone was the tentative approach of the previous year; in its place a new confidence and authority fostered by Kleiber's own love for and intimate knowledge of the score, were added to the womanly warmth and dignified resignation already featured in her characterisation of the Marschallin.
In 1952 Sylvia Fisher made her Italian debut, singing Sieglinde at the Rome Opera, where Kleiber was again the conductor. She also sang Gutrune in Bologna , native city of her husband, the violinist Ubaldo Gardini, whom she married in 1953.
Meanwhile in January that year Fisher tackled her most ambitious assignment so far: Isolde. First she went to Berlin to study the part with Frieda Leider, one of the greatest Isoldes of the previous generation. Although certain critics forecast that the role would be too heavy for her, Sylvia Fisher's Isolde was a great success.
The authority she had gained in singing the Marschallin with Kleiber now stood her in good stead, especially in the first act, where her vehemence surprised some of those same critics, while in the second-act love duet she surpassed all expectations with the fervour and beauty of her singing. The conductor on that occasion was Sir John Barbirolli.
During the next five seasons Fisher took on seven new roles. Agathe in Der Freischutz and Elisabeth in Tannhauser were splendidly sung, but did not make much dramatic impact, perhaps because of the weakness of the productions. Ellen Orford in Peter Grimes, though, was a role that might have been written expressly for the Australian soprano, who conse-quently was at her very best in it. She gave another excellent and extremely powerful performance as the Kostelnicka in Jancek's Jenufa and, not for the first time, surprised everyone by the sheer splendour of her sing-ing in the title role of Puccini's Turandot, her only Italian part.
Even more surprising was her mastery of a part that she sang on the Covent Garden Company Spring Tour, but never in London. On 13 March 1956 the Theatre Royal, Birmingham was filled with Sylvia Fisher's admirers, who had come to hear her sing her first Brunnhilde in Die Walkure; the conductor was Reginald Goodall, and although the consensus of opinion was that Sieglinde remained her finest Wagner role, Fisher's Brunnhilde, ardently sung and characterised with youthful enthusiasm, roused great admiration.
Her last new role at Covent Garden for many years was Mere Marie in Poulenc's Dialogues des Carmelites, another resounding success. Although no longer a member of the company, she returned three times during the next five seasons to sing Mere Marie.
In 1958 Fisher returned to Australia to appear with the Elizabethan Theatre Trust in Peter Grimes and Jenufa. On her way back to the UK she stopped off at Chicago in November 1959 to sing the Kostelnicka, making her American debut.
Meanwhile a new chapter of her career was opening with the English Opera Group: she sang Lady Billows in Albert Herring at Aldeburgh, Mrs Grose in The Turn of the Screw and the Female Chorus in The Rape of Lucretia at the Edinburgh Festival and, on 23 November 1963, the title role of Gloriana at a concert performance in the Royal Festival Hall, given in celebration of the composer's 50th birthday the previous day.
The huge success of this event had equally important consequences. For the first time Britten's Coronation opera was recognised as a master-piece. Three years later a new production was staged at Sadler's Wells and Sylvia Fisher, who had scored a great personal triumph at the Festival Hall concert, again sang Gloriana.
The role became the finest achievement of the second half of her career; with each revival her characterisation grew, both in authority and in emotional intensity, culminating in 1972 when Gloriana transferred to the London Coliseum, where Sadler's Wells Opera, shortly to become English National Opera, was now based, and was toured to the Theater am Gartnerplatz in Munich. Fisher also sang the Kabanicha in Katya Kabanova for ENO, a truly terrifying portrait of repressive tyranny.
Her last role at Covent Garden, in 1973, was Miss Wingrave, another study in repression, which she had created in Britten's television opera Owen Wingrave two years previously. This performance exists on video and on disc, otherwise Sylvia Fisher is badly represented in the record catalogues. There is a bracing and bossy Lady Hillows available in a complete Albert Herring and that is about all. Her Marschallin, her Sieglinde, her Isolde, her Ellen Orford and her Gloriana are still vivid in the memory of those lucky enough to have seen and heard them.
Sylvia Fisher, opera singer: born Melbourne, 18 April 1910; married 1953 Ubaldo Gardini; died 25 August 1996.