Sundelius began performing professionally in concerts and oratorios in Boston in 1910, making her debut performance under the baton of Karl Muck.
Karl Marx | Karl Pilkington | Karl Lagerfeld | Karl G. Heider | Karl Rove | Karl Pearson | Karl May | Karl Liebknecht | Karl Friedrich Schinkel | Karl Dönitz | Karl Jenkins | Karl Stefanovic | Karl Bodmer | Karl Wilhelm Friedrich Schlegel | Karl Malone | Karl Wolf | Karl Valentin | Karl Popper | Karl Malden | Karl Kesel | Karl Barth | Karl Richard Lepsius | Karl Philipp von Wrede | Karl Kautsky | Karl Johans gate | Karl-Heinz Kämmerling | Karl | Karl Weierstrass | Karl Story | Karl Scheel |
In 1908 Karl Muck, then the conductor of the Boston Symphony Orchestra, recommended Fiedler as his successor as conductor of the orchestra, and he was duly appointed, having already appeared in the United States during 1905, when he had conducted the New York Philharmonic Orchestra alongside Willem Mengelberg and a year before the guest appearance of a German conductor noted for his Brahms, Fritz Steinbach.