[1] Sissel's musical style runs the gamut from pop recordings and traditional folk songs, to classical vocals and operatic arias.
She possesses a "crystalline" voice[2] and wide vocal range, sweeping down from mezzo-soprano notes, in arias such as Mon cœur s'ouvre à ta voix from Saint-Saëns's opera Samson et Dalila, to the F natural above soprano C.[3] Sissel has sung duets with singers like Plácido Domingo, José Carreras, Andrea Bocelli, Bryn Terfel, Josh Groban, Neil Sedaka, Mario Frangoulis, Russell Watson, Brian May, Tommy Körberg, Diana Krall, Warren G, Charles Aznavour, Dee Dee Bridgewater and The Chieftains.
She sings mainly in English and Norwegian, and has also sung songs in Swedish, Danish, Irish, Italian, French, Russian, Icelandic, Faroese, German, Neapolitan, Maori, Japanese, and Latin.
Her participation on the Titanic film soundtracks, singing the Olympic Hymn (Hymne Olympique) at the opening and closing ceremonies of the 1994 Winter Olympics in Lillehammer, Norway, and the tour with the Lord of the Rings Symphony has made her voice familiar to people all over the world.
Let It Snow!/Let There Be Peace on Earth/We Wish You a Merry Christmas") ("Et barn er født i Betlehem/Her kommer dine arme små/Det kimer nå til julefest/Jeg synger julekvad")