Lee's vocal range spans 3.6 octaves from a low A2 (2003 Fallen Vocal warm up) to an E6 in full head voice (MTV Video Diary). Her highest recorded note in full head voice is a C#6 in the song “Weight of the World" and her lowest recorded note is a C3 in the cover of U2's song “With or Without You". Lee's highest mixed note in studio recording is a G#5 in the collaboration with American rock band Halestorm's song “Break In”. Overall, her highest mixed note is a Bb5 in a cover of Michael Jackson's song “Dirty Diana". Lee has also been known for her scream in the song “Tourniquet” also, in which is in the note of a D5. In an MTV special, Lee managed to hit an E6 live during a vocal warm-up in full head voice, also showing that she is capable of reaching up to Bb7 through exclamation. She is popularly classified as a full-lyric mezzo-soprano, though this has not been confirmed by Lee herself.