Iles broadcast frequently for the BBC, and appeared as concerto soloist with distinguished conductors including Sir Thomas Beecham, Sir Adrian Boult, and Willem Mengelberg.
He remained with the orchestra for eight years, playing under Wilhelm Furtwängler and guest conductors including Bruno Walter and Willem Mengelberg.
After graduating in 1940, he became violinist with the National Radio Orchestra of Romania, where he was noticed by the conductor, Willem Mengelberg; Voicu made his debut as a soloist with the orchestra soon after.
In 1921 the Philharmonic merged with the National Symphony, conducted by Willem Mengelberg.
For several years he lived in the Netherlands and from 1940-1942 he was first violinist of the Royal Concertgebouw Orchestra under Willem Mengelberg.
Willem de Kooning | Willem Dafoe | Willem Blaeu | Willem Janszoon | Willem Mengelberg | Willem Roggeman | Herman Willem Daendels | Willem Drees | Willem-Alexander of the Netherlands | Misha Mengelberg | Willem van Otterloo | Willem Schouten | Willem Kloos | Willem Klein | Willem II (football club) | Willem II | Willem de Vlamingh | Willem Buiter | John Willem Gran | Willem Verstegen | Willem van Hoogstraten | Willem van Enckevoirt | Willem van de Sande Bakhuyzen | Willem Sassen | Willem P.C. Stemmer | Willem Frederik Hermans | Willem C. Vis Moot | Willem B. Drees | Willem Abraham Wythoff | Pieter Willem Korthals |
Before long, she was performing all over Europe and America, sharing the stage with such notable composers, conductors and singers as Edvard Grieg, Richard Strauss, Camille Saint-Saëns, Enrico Caruso, Otto Klemperer, Willem Mengelberg, Pablo Casals, Percy Grainger, Enrique Granados and Thomas Beecham.
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.
Karel Mengelberg (1902–1984), Dutch composer and music writer, nephew von Willem Mengelberg