Royal Concertgebouw Orchestra
As well as their chief conductor, the orchestra had assistant conductor positions called “first conductor” and “second conductor”.  During Mengelberg’s time the “first conductors”  included  Karl Muck (1921-1925), Pierre Monteux (1924-1934), Bruno Walter (1934-1939), and Eugen Jochum (1941-1943), and the second conductors included the composer Cornelis Dopper, Evert Cornelis and Eduard van Beinum.