He was regarded among Scandinavia"s leading pianists, and toured all over the western world. He was a Professor in Copenhagen from 1967, and in Oslo from 1973. Riefling made his concert debut with the Oslo Philharmonic in Kristiania in 1922, and had his solo debut in 1925.
He studied piano in Oslo with Nils Larsen, and from 1928 in Germany with Karl Leimer, Wilhelm Kempff and Edwin Fischer.
During the occupation of Norway by Nazi Germany he was arrested and held at Bredtveit and Grini concentration camp a few months in 1942 and 1943. He was widely known for his interpretation of works by Johann Sebastian Bach, including The Well-Tempered Clavier, which he had studied while being imprisoned, and played at concerts in Oslo, Copenhagen and London in 1947.
He recorded more than 60 albums, including all Beethoven"s sonatas, sonatas by Joseph Haydn and Mozart, and all works by Fartein Valen. Among his first performances of contemporary compositions are Klaus Egge"s Fantasi i Halling, a piano concert by Harald Sæverud and Johannes Rivertz" piano suite Spill og dans.
In 1967 he was appointed Professor at the Royal Danish Academy of Music in Copenhagen, and a Professor at the Norwegian Academy of Music from its establishment in 1973.