Karajan's selection of a lighter soprano voice (Helga Dernesch) as Isolde, paired with an extremely intense Jon Vickers and the unusual balance between orchestra and singers favoured by Karajan was controversial.
A selección realizada por Karajan dunha soprano lixeira (Helga Dernesch) como Isolde, xunto cun extremadamente intenso Jon Vickers, sumado a un infrecuente balance entre orquestra e os cantantes favoritos de Karajan foi motivo de controversia.