Leonie Rysanek was a highly individual soprano with a voice instantly recognisable. It was characterised by a uniquely thrilling top which made her particulary well suited to Strauss's Empress, a role which she was closely associated with for many years. Lower down the voice was less attractive. It had an almost mezzo-ish quality, a fairly weak patch towards to the bottom, often sounded hollow, and had a tendency to poor intonation. Consequently, her studio recordings often don't do her justice. She was a highly intense and charismatic actress, however, and was wildly popular at the New York Metropolitan.

The Empress was Rysanek's most famous role by far, and she specialised mainly in Strauss roles (Chrysothemis, Salome, Helena) and Wagner (Sieglinde, Kundry, Senta). She also sang some Verdi, however: she is a rather unusual Desdemona opposite Jon Vickers on Serafin's 1960 recording for RCA, and also sang Lady Macbeth (the role with which she first impressed the audience at the Met) and Amelia (Un Ballo in Maschera). In the mid eighties she turned to mezzo roles, including Klytämnestra (thus achieving the unusual distinction of having sung all three main roles in Elektra), Herodias, Countess (The Queen of Spades), Kostelnicka, and Kabanicha.