On 15 May 1924 Paul Hindemith married Johanna Gertrude Rottenberg, called Gertrud. The witnesses were the artistic director of the Frankfurt Radio, Dr. Hans Flesch, who was married to Gertrud's elder sister Gabriele, and the painter Rudolf Heinisch.
Gertrud was the daughter of the principal conductor of the Frankfurt Opera, Ludwig Rottenberg, under whom Hindemith served as concertmaster. On her mother's side, Gertrud hailed from the respected family of the Frankfurt mayor Franz Adickes. She was born on 2 August 1900 in Frankfurt born and, after attending school in Frankfurt and Paris, received training as a singer and actress. She participated in performances in Mainz and Heilbronn, and also took on roles in film productions. Her career faltered, however, due to stage fright; Gertrud's stage appearances after her marriage were therefore limited to ensemble and choral performances. (G. Skelton)
The Hindemiths lived together with Sophie and Toni Hindemith in the Cowherds' Tower, occupying the two topmost storeys. Gertrud und Paul, whose marriage remained childless, made a great deal of music together and gave house music evenings for which Hindemith wrote small pieces. Gertrud played the cello especially often on these occasions.
Gertrud saw it as her task to stand by Hindemith's side in his artistic work. She took over part of the business correspondence and the organisation of his concert tours, on which she usually accompanied him.
After Hindemith's death in December 1963, Gertrud began organising his estate in order to prepare a Hindemith Archive. She died on 13 March 1967 and was interred next to Paul Hindemith near their final residence near Blonay in St. Légier.
Hindemith drew Gertrud in countless caricatures, represented as a lioness in accordance with her Zodiacal sign. This can be found in letters to her and in several scores. At the villa «La Chance», the last residence of the Hindemiths in Blonay, the lion even adorns the house walls and a garden hut. Hindemith dedicated several works to Gertrud: Kammermusik No.4, songs with piano accompaniment to texts of Angelus Silesius, the Serenades and Das Unaufhörliche.