He wrote a serious opera called Saul og David and a comic opera Maskarade . The four-act Saul og David ( Saul and David ) , written in 1902 to a libretto by Einar Christiansen tells the Biblical story of Saul 's jealousy of the young David while Maskarade ( Masquerade ) is a comic opera in three acts written in 1906 to a Danish libretto by Vilhelm Andersen , based on the comedy by Ludvig Holberg . While Saul og David is one of Denmark 's most important musical works for the theater , it is difficult to stage as the really dramatic episodes are often separated by longer , less dynamic sequences .