Although she was born in Sweden, this imposing contralto was of French and German stock and was reared in Germany, where she began her vocal studies. Noted for her extensive range and exceptional flexibility, she made her reputation first in concert work before achieving similar distinction on the operatic stage. Brought up in Wiesbaden, the singer undertook her initial studies there. Later, she traveled to Frankfurt to further her training before she worked with E.R. Weiss in Munich and with Di Ranieri in Milan. She also had the benefit of advice from the formidable Lilli Lehmann, whose concern for keeping the voice well-placed and pliant aided the contralto in her performances of bel canto composers. She also briefly studied with Margarete Siems, remembered for her performances in the premieres of operas by Richard Strauss. Although she had made her operatic debut as early as 1912 when she sang Carmen in Stuttgart, she became better-known as a concert singer, having begun that aspect of her career the same year as her first stage appearances. Not until an engagement with the Munich Hofoper from 1919 to 1922 did her fame as a dramatic artist begin to match that accorded her recital work. Having initially sung as Lilly Hoffmann, she later added the name of her husband, the Baron Yevgeny Borisovitch Lvov Onégin (a pianist and composer who had taken the name of Pushkin's famous anti-hero) and sang as Lilly Hoffmann-Onégin. The final transition came after her husband's premature death when she assumed the name Sigrid Onégin, retaining it despite her marriage to Dr. Fritz Penzoldt in 1920. Onégin made her first visit to the United States in 1922, making her American debut with the Philadelphia Orchestra led by Leopold Stokowski and shortly thereafter appearing at the Metropolitan Opera. Following her performance of Amneris in a November 22, 1922, Aida (the same night that introduced Elisabeth Rethberg to a Metropolitan audience), The New York Times described her as "a woman of majestic grace, broad gesture, brooding calm...stirred with the gleam of temperamental fire." W.J. Henderson had already weighed in with a verdict after her October 23 orchestral performance, finding hers "a truly noble voice" and praising her "tragic intensity" and "large style." Pitts Sanborn was reminded of tales about Maria Malibran and Pauline Viardot and their enormous ranges: "Mme. Onégin's illimitable voice achieves the prodigious peculiarity of seeming to be both a contralto and a soprano, and its astonishing flexibility (who since Melba and Tetrazzini has displayed such a trill?) places the most florid music easily within her scope." Onégin remained at the Metropolitan Opera for just two seasons, winning further praise for her Brangäne and Fricka. Her Covent Garden debut came in 1927 when she sang Fricka in a May 6 performance of Die Walküre. Ernest Newman described her as "perhaps a little too commanding physically and temperamentally for the role, though her voice, presence, and style were all excellent." In her single London season, Onégin was also heard as Waltraute, Brangäne, and Amneris, the latter part thought "superbly" sung by at least one critic. While continuing to perform in concert, Onégin essayed Gluck's Orfeo in 1931 and 1932 at the Salzburg Festival and appeared at Bayreuth in 1933 and 1934 as Fricka, Waltraute, and Erda.