Willem Mengelberg
Bustabo toured Europe and Asia. She performed under top-rank conductors, including Sir Thomas Beecham, Issay Dobrowen, Albert Coates, Hermann Abendroth, Wilhelm Furtwängler, Oswald Kabasta, Herbert von Karajan and Willem Mengelberg. Blanche Bustabo decided that Guila would remain in Europe and perform in Germany and Nazi-occupied countries during World War II.