In 1938 he became the representative leader of the Reichs-authority for Musical Activities in the Reichs-Ministry of Public Enlightenment and Propaganda; from 1940 until 1945 he was its General Secretary.
He received in 1947 a professorship from the Jena University, but after two months it was withdrawn in the light of his activities in the Propaganda Ministry.
Moser wrote studies of numerous composers, like Paul Hofhaimer, Heinrich Schütz und Johann Sebastian Bach as well as his studies in Das deutsche Lied seit Mozart (German Song since Mozart) of 1937.
Moser carried out the new editing of the Monuments of German Composition (Denkmäler deutscher Tonkunst, or DDT).
Moser's oeuvre as a composer includes piano pieces, songs, theatre music and choral works.