Schubert was born in Dessau where he studied with Franz von Hoesslin and Arthur Seidl and in Munich with Hugo Röhr and Heinrich Kaminski.
After the Machtergreifung by the Nazis in 1933, he joined the National Socialist German Workers' Party under the number 3.119.361[1][2] and became Kapellmeister in Flensburg in the same year.
In 1936, his oratorio Das ewige Reich based on a text by Wilhelm Raabe for baritone, male choir and organ, was premiered.
Schubert came under increasing pressure in the early 1940s due to his inner distance to the regime, but he remained largely undisturbed by the influence of his patron Wilhelm Furtwängler until shortly before the end of the war.
[6] In the course of the rediscovery of composers such as Heinrich Kaminski and Reinhard Schwarz-Schilling, Schubert's work has recently received late recognition, which is reflected in the reprints of several compositions.