He was born in Kongsberg and studied music first in Oslo before going to Germany, where he studied at the conservatory in Leipzig under Salomon Jadassohn and fell under the musical influences of Wagner and Liszt. He lived in Germany for much of his life, but received regular grants from the Norwegian government. In 1920–21 he went to the United States of America to teach composition for a season at the Eastman School of Music in Rochester, New York. In 1924 he was given Henrik Wergeland’s Oslo home, "Grotten" ("The grotto"), as an honorary residence. He died in Oslo.
Sinding's publishers required from him piano and chamber music, which has broader sales than the symphonic works he preferred. His own instrument was the violin. The large number of short, lyrical piano pieces and songs that Sinding wrote has led to many seeing him as the heir to his fellow countryman, Edvard Grieg, not so much in musical style but as a Norwegian composer with an international reputation. After his first piano sonata was premiered, a critic complained that it was "too Norwegian". Though Sinding is said to have replied that the next one would be even more so, specifically Norwegian folk-elements are not prominent in his richly contrapuntal post-Wagnerian orchestral style.
Sinding is best remembered today for one of his piano works, Frühlingsrauschen (Rustles of Spring, 1896). Among his other works — which are rarely performed, as Grieg overshadowed Sinding — are three symphonies, three violin concertos, a piano concerto, chamber music, songs and choral works to Norwegian texts, and an opera, Der Heilige Berg (The Holy Mountain, 1914).
In 1941, eight weeks before his death, Sinding was entered into the Norwegian Nazi party, Nasjonal Samling. This largely explains his relative obscurity in Norway since - it was official practice for the national broadcasting monopoly after the war to boycott people seen as Nazi sympathisers. The circumstances surrounding his membership are to say the least very controversial. His fees were to be paid by the party. He had made several remarks against the occupation, had fought for the rights of Jewish musicians during the early 1930s, was a close friend of the war hero Nordahl Grieg, and had since the late 1930s suffered from severe senile dementia. The motives for the Nazi party for getting Sinding into the party were obvious - he was a tremendously popular composer before the war, particularly in Norway and Germany.
"Frühlingsrauschen" ("Rustles of Spring") was quoted by Meredith Willson in his musical The Music Man, was one of the main themes of Dennis Potter's 1986 miniseries The Singing Detective, and was sampled by hip-hop producer 4th Disciple on Killarmy's track "Wu-Renegades." A hundred years ago it enjoyed a vogue, along with other now-forgotten pieces like Tchaikovsky's Chant sans paroles, Anton Rubinstein's Melody in F, Scharwenka's Polonaise in E-flat minor, Paderewski's Minuet in G, and Leybach's Fifth Nocturne, all of which were invariably found in collections with titles like "World's Greatest Piano Pieces." Today little of this music is heard.