In the 1930s, Messner smoothed out his otherwise revolutionary tonal language by replacing his "dissonant counterpoint" with the "melodious sounds of the tonic triad".
In 1934, he took part in the film Das unsterbliche Lied [de], which tells a Christmas story around the song Silent Night.
In his career, he felt ignored or thwarted on several occasions, for example in 1946 when he was appointed rector of the Mozarteum Academy of Music and at his cathedral concerts, which were removed from the official festival programme in 1968.
Messner died unexpectedly in 1969 in his family home in St. Jakob am Thurn at the age of 75, where he had lived for several decades with the singer Evi Klemens.
In addition, he composed three symphonies (in C minor, F major and A major), several instrumental and orchestral works (including the Salzburg Suite, which describes as a programme various sights in Salzburg), four operas (including one about the person of Esther), numerous Lieder and a large number of sacred works (masses, proprium music, motets, sacred songs, etc.).