The march that you mention (' King Frederick Ninth') it doesn't figure in the Danish composer's Carl Neilsen catalog: http://members.aol.com/dmlovelock/nielsen_fog.htm But I have another doubt, is the work 'Helios' of Nielsen, 1923, only an overtura or did he carry out a complete opera? Other Operas: - Saul og David, ' Saul and David', (1898-1901). it Operates in four acts, libretto by E. Christiansen after the First and Second Books of Samuel. - Maskerade, ' Masquerade', (1904-06). Comic operates in three acts, libretto by V. Andersen after the play by Holberg. [You can find many pictures in http://www.mic.dk/nielsen] Best regards, Alberto Cobo www.superopera.com