As first violin of the Busch String Quartet, founded in 1912, he was the greatest quartet-player of the last century and he led a famous conductorless orchestra, the Busch Chamber Players. He was also the busiest solo violinist of the inter-War years, regularly performing major concertos with such conductors as Nikisch, Toscanini, Weingartner, Walter, Furtwaengler, Boult, Wood, Barbirolli and his elder brother Fritz.