Rued Langgaard (Danish: [ʁuðˀ ˈlɑŋɡ̊ɒːˀ]; born Rud Immanuel Langgaard; 28 July 1893 – 10 July 1952) was a late-Romantic Danish composer and organist. His then-unconventional music was at odds with that of his Danish contemporaries and was recognized only 16 years after his death.
Born in Copenhagen, Rued Langgaard was the only son of composer and Royal Chamber musician Siegfried Langgaard (1852–1914) and Emma Langgaard (née Foss, 1861–1926), both of whom were pianists. At the age of five Rued began taking piano lessons with his mother, and later with his father and a private teacher. His talent emerged quickly, and at seven he was able to play Schumann's Davidsbündlertänze and Chopin's mazurkas. By then he had begun to compose short pieces for the piano and play the organ. At 10 he began to study the organ under Gustav Helsted, organist at the Jesuskirken in Valby, and the violin under Chr. Petersen, formerly of the Royal Orchestra.
At the age of 11 he made his first public appearance as an organist and improviser on the organ at a concert at the Frederikskirken (Marmorkirken) in Copenhagen. When he was 12, he started to study music theory under C. F. E. Horneman and, later, Vilhelm Rosenberg.
Langgaard's first compositions, 2 piano pieces and 2 songs, were published when he was 13, and around that time he was taught counterpoint by the celebrated composer Carl Nielsen for about a month. A year later, his choral work Musae triumphantes was performed at a concert in Copenhagen, marking his public debut as a composer. During his teen years he continued composing and travelled with his parents around Christmas and New Year's Eve, meeting conductors Arthur Nikisch and Max Fiedler.