Willem Mengelberg (1871-1951) was the conductor of the Royal Concertgebouw Orchestra.
In 1902 he met Gustav Mahler and became friends with him; he introduced most of Mahler's work to the Netherlands, and founded the long-standing Mahler tradition of the Concertgebouw Orchestra.
Mahler regularly visited The Netherlands to introduce his work with the Dutch audience. In fact, he edited some of his symphonies while in the Netherlands making them sound better for the acoustics of the Concertgebouw, which is maybe one reason that this concert hall and its orchestra is renowned for its Mahler tradition.