Dimmu Borgir started to experiment after 1999 .
Significant experimentation started c. 2000 , during the era of Spiritual Black Dimensions ( due to the addition of Vortex 's clean vocals , and the variety of musical ideas from then-new member Mustis ) , as well as Puritanical Euphoric Misanthropia due to addition of influences from composers such as Antonín Dvořák , Enya , Richard Wagner and Frédéric Chopin .
Dimmu Borgir