Ernst Krenek (August 23, 1900 – December 22, 1991) was an Austrian, later American, composer of Czech origin. He explored atonality and other modern styles and wrote a number of books, including Music Here and Now (1939), a study of Johannes Ockeghem (1953), and Horizons Circled: Reflections on my Music (1974). Krenek wrote two pieces using the pseudonym Thornton Winsloe.
Krenek was born in Vienna (then in Austria-Hungary) as Ernst Křenek (Czech pronunciation: [ˈkr̝ɛnɛk]) as the son of a Czech soldier in the Austro-Hungarian army. He studied there and in Berlin with Franz Schreker before working in a number of German opera houses as conductor. During World War I, Krenek was drafted into the Austrian army, but he was stationed in Vienna, allowing him to go on with his musical studies. In 1922 he met Alma Mahler, widow of the late Gustav Mahler, and her daughter, Anna, to whom he dedicated his Symphony No. 2, and whom he married in March 1924. That marriage ended in divorce before its first anniversary.
At the time of his marriage to Anna Mahler, Krenek was completing his Violin Concerto No. 1, Op. 29. The Australian violinist Alma Moodie assisted Krenek, not with the scoring of the violin part, but with getting financial assistance from her Swiss patron Werner Reinhart at a time when there was hyper-inflation in Germany. In gratitude, Krenek dedicated the concerto to Moodie, and she premiered it on 5 January 1925, in Dessau. Krenek’s divorce from Anna Mahler became final a few days after the premiere. Krenek did not attend the premiere, but he did have an affair with Moodie, which has been described as "short-lived and complicated". He never managed to hear her play the concerto, but he did "immortalize some aspects of her personality in the character of Anita in his opera Jonny spielt auf". This 'jazz opera', completed in 1926, was an enormous success across Europe and made Krenek a household name for several years; there was even a brand of cigarettes, still on the market today in Austria, named "Jonny". Krenek himself became uncomfortable with this success though, as his musical colleagues criticised the commercialisation of his music, and shortly afterwards changed his compositional direction radically.