Birgit Nilsson, who has died aged 87, was considered to be the greatest Wagnerian soprano of her day; she had a rock-solid technique and a voice of such soaring, unforced power that it was able to cut through the massed forces of a Wagnerian orchestra with ease, yet a purity of tone which enabled her to switch to the most delicate pianissimo.

She sang a wide variety of dramatic soprano roles, but her reputation was based on her mastery of some of the most punishing in the repertory – Brunnhilde, in Wagner’s Ring cycle, which she sang on her debut at London’s Covent Garden in 1957 and Isolde in Wagner’s “Tristan und Isolde,” which she sang at her Met debut in 1959, an event that confimed her as a successor to Kirsten Flagstad, the Norwegian soprano who had dominated the Wagner repertory before the war. She excelled also as Elektra in Richard Strauss’s opera of that name and as the fire-andice heroine of Puccini’s “Turandot.”

Nilsson’s extraordinary vocal power and breath control enabled her to hold on to flawless high notes for almost unnatural lengths of time, a facility which involved her in frequent battles of climactic high Cs with the almost equally dazzling tenor Franco Corelli. A story is told of how, on one occasion during the second act of Turandot, Corelli was so enraged at being unable to sustain his top note for as long as hers that he took his revenge by biting her on the neck during their love scene in the third act. Nilsson is said to have pulled out of the next performance, explaining: “I have rabies.”

An only child, Marta Nilsson was born on May 17, 1918, on a farm at Vastra Karup, Sweden, a small coastal town 60 miles north of Malmo. She studied at at Stockholm’s Royal Academy of Music over the objections of her father, who did not want her to pursue a singing career, hoping that she would take over the farm that had been in the family for six generations.

She won her first contract at at Stockholm’s Royal Opera House in 1947, learning the role in three days. Her performance won her an immedi ate contract and in 1947, as Lady Macbeth in Verdi’s “Macbeth.” Her British debut at Glyndebourne in 1951 as Elettra in “Idomeneo” and subsequently sang in Vienna and Bayreuth, where she made her debut as Elsa in Lohengrin in 1954 and returned as Isolde in 1957, beginning a long association with the festival that lasted until 1970 and saw her take on the roles of Brunnhilde and Sieglinde as well.

She scored one of her greatest successes in 1958 in front of the famously demanding audience at La Scala in Milan, when her portrayal of the cruel Princess Turandot, given an extra edge by her Scandinavian coolness, brought the house down.

Her American debut was as Brunnhilde in “Die Walkure” at San Francisco in 1956,though it was her first performance as Isolde at the Met that confirmed her status as a leading inter national star. Her portrayal won her a standing ovation lasting 15 minutes, after which she blithely announced that she could “sing Turandot right now.”

Small but sturdily built, Nilsson retained the robust constitution and no-nonsense approach of the strapping farmer’s daughter. She was known to gulp down pints of Guinness between scenes of Strauss’s Elektra and often regretted that she could not take her beloved horses and dogs on tour with her. Even at the height of her international career, she would take time out to return home and milk the cows.

In 1959 at the Met, she famously “outsung” three different Tristans, who all pleaded illness but were prevailed upon to take her on for one act apiece so that the performance would not have to be cancelled. Once asked what was the chief requirement for singing the role of Isolde, she replied: “Comfortable shoes.”

Nilsson’s vivacious, straight-talking approach was not always appreciated by her conductors. On one occasion Herbert von Karajan,annoyed at her refusal to show him the deference he thought was his due (she called him “Herbie”), retaliated by sneering that she could play Scarpia, the sadistic police chief in Puccini’s Tosca, without needing to put on any make-up.Nor did von Karajan appreciate the joke when, during a rehearsal of the Ring, she appeared on stage wearing a miner’s helmet, in protest at the gloomy lighting on which he had insisted for the production.

Nilsson retired from the operatic stage in 1982, though she continued to teach master classes in singing. In 1992 she came out of retirement to sing Brunnhilde at a gala performance at Covent Garden. Her few bars of “Ho-joto-ho! Heia!” showed that, at 72, she could still tingle the spine with the voice that had dominated opera houses in the 1960s and 1970s.