Manns was able to prevail in the subsequent application process against strong competition, such as a nephew of Max Bruch and a Hamburg choral conductor recommended by Johannes Brahms.
He was faced with the difficult task of consolidating and expanding the level of the court orchestra achieved by his predecessor.
According to his biographer Ernst Hinrichs, who refers to contemporary press reports, he did not succeed in this, although he was able to set new, more contemporary accents compared to his predecessor's concert practice, which was focused on Schumann and Brahms, and above all opened the way for music by Bruckner and Tchaikovsky to be performed in Oldenburg.
In addition, the equipment of the court orchestra at the beginning of the 20th century no longer met the requirements that the new compositions (for example Anton Bruckner, Richard Strauss, etc.)
Manns retired in 1913 and was awarded the title of professor by Grand Duke Friedrich August for his services to Oldenburg's musical culture.