Given the following context:  From 1916, Nielsen taught at the Royal Academy where he became director in 1931, shortly before his death. He also had private students in his earlier days in order to supplement his income. As a result of his teaching, Nielsen has exerted considerable influence on classical music in Denmark. Among his most successful pupils were the composers Thorvald Aagaard, remembered in particular for his songs, Harald Agersnap, both a conductor and orchestral composer, and Jørgen Bentzon who composed choral and chamber music mainly for his folk music school (Københavns Folkemusikskole). Among his other students were the musicologist Knud Jeppesen, the pianist Herman Koppel, the academy professor and symphony composer Poul Schierbeck, the organist Emilius Bangert who played at Roskilde Cathedral, and Nancy Dalberg, one of Nielsen's private students who helped with the orchestration of Aladdin. Nielsen also instructed the conductor and choirmaster Mogens Wöldike, remembered for his interpretations of Baroque music, and Rudolph Simonsen, the pianist and composer who became director of the Academy after Nielsen's death.The Carl Nielsen Society maintains a listing of performances of Nielsen's works, classified by region (Denmark, Scandinavia, Europe apart from Scandinavia and outside Europe) which demonstrates that his music is regularly performed throughout the world. The concerti and symphonies feature frequently in these listings. The Carl Nielsen International Competition commenced in the 1970s under the auspices of the Odense Symphony Orchestra. A four-yearly violin competition has been held there since 1980. Flute and clarinet competitions were later added, but these have now been discontinued. An international Organ Competition, founded by the city of Odense, became associated with the Nielsen competition in 2009, but from 2015 will be organized separately, based in Odense Cathedral.  answer the following question:  What is the last name of the person that taught Knud Jeppesen?
Nielsen