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In page Elisabeth Schumann:

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Despite her glittering operatic career, she excelled in lieder. Lotte Lehmann, in many ways her rival, paid her the tribute of saying that she represented perhaps the purest singing style of German lieder.[citation needed] The production of her voice, which was not particularly powerful, enabled her to continue giving recitals long after many singers retire. This is most evident in her rendering of Schubert's "Du bist die Ruh" which requires a steadiness and purity of tone beyond most singers.[3] This technique sustained her in dramatic operatic roles like Der Rosenkavalier. Her careful use of vibrato, never coarse, gave volume and sonority.