He was held at Ruhleben internment camp during World War I.
He made many recordings of the works of Mahler and Anton Bruckner.
He made the first commercial recordings of Mahler's Third and Sixth symphonies.
(Hans Knappertsbusch was the only other major conductor to stick with the first editions consistently.)
[3] Adler also promoted much modern music, both in the SPA Music Festival he led in Saratoga Springs, New York and for various record labels (including SPA, Unicorn, and CRI).