Riisager studied political science, but at the same time took private lessons in music theory from Otto Malling and Peder Gram. When he had completed his law studies he went to Paris for further studies in music theory with Albert Roussel and others. The years in Paris were crucial to his activities as a composer. He cultivated a French-inspired treatment of instrumentation and timbre, and remained a devotee of "Gallic" clarity in music. Lightness and gaiety are characteristic of his smallest works, but his elegance and masterly treatment of the instruments function brilliantly even in the largest works. Best known are his ballet works 'Etudes', 'Slaraffenland', 'Qarrtsiluni', which were created in collaboration with the great Danish choreographer Harald Lander, and the ballet 'Tolv med Posten' in collaboration with Børge Ralov . Many of his children's songs are still on the lips of Danes. Riisager was a cultured, intellectual figure and a lively debater. The fact that he drew inspiration from Central European Modernism was of great importance to Danish music. Along with other contemporary Danish composers who had studied abroad he definitively broke with Romanticism as well as the epigonism of Carl Nielsen's disciples.
