Leden was interested in the early music of
Kalaallit (Greenland's
Inuit). In the spring of 1909, he received travel funds from the Danish
Carlsberg fund to go to northern Greenland to study
Inuit music on a voyage with the Danish polar scientist
Knud Rasmussen. In the autumn of that year, he returned to Europe and worked on the music he had collected. He traveled in
Northern Canada in 1911, West Greenland in 1912, and through the
Keewatin Region,
Northwest Territories (now
Kivalliq Region,
Nunavut) in 1913. a three-year expedition to the Keewatin Region on the west coast of
Hudson Bay, he went to several villages collecting everything he could, from art to everyday objects. Leden cataloged his collection with each item's
Inuktitut name and English name, as well as its function. In 1919, American whaler
George Comer was captain of Leden's chartered voyage to study amongst the Inuit. Their schooner, the
Finback, grounded at
Cape Fullerton and was lost. Fortunately, everyone survived. The following year, Leden was on another expedition that wrecked on a reef in
Hudson Bay. He traveled to East Greenland in 1920 and 1926. In 1949 and 1954, he traveled in South America, including Chile, Argentina, and
Easter Island, but the materials he collected during these expeditions were neither edited or published though he recorded thirteen songs on nine wax cylinders. He also worked to preserve Norwegian
folk music, traveling the country in 1937-1938 making recordings. Leden received support from the
Geological Survey of Canada who helped him to continue his ethnographic work over several years. His expeditions were sponsored by the King and Queen of Norway, the
University of Christiania, and the Danish Carlsberg fond. His work was compiled in the
Danish Folklore Archives, and was later transferred to the
Royal Danish Library. Some of his recordings are housed at the
Musée d'ethnographie de Neuchâtel. Leden wrote several articles that were published in journals, including "Christmas Among the Eskimos", "Trapping Salmon in the Far North", "A Chapter from my Eskimo Travels", and "Mobilizing the Arctic". In the 1930s Leden became involved in
Nazi German racial research, meeting with amongst others the leading Nazi racial theorist
Hans F. K. Günther in Berlin. Leden joined the racial theorist organization
Nordischer Ring c. 1930. He also had contacts with national socialist organizations both in Germany and Norway, including the SS
Ahnenerbe think tank. He also worked for the
Völkischer Beobachter, and in 1940 joined the foreign branch of the Norwegian national socialist party
Nasjonal Samling. His Nazi connections is part of the reason his work is relatively unknown in Norway. ==Personal life==