Nielsen composed the quartet, Op. 44, between two of his major achievements: the opera Maskarade and the music for the melodrama Hr. Oluf han rider–. The first two movements of the quartet are dated at the beginning of 1906, while the last two ones were finished in the summer. It seems that the quartet was revised several times, between different performances (1906–12) and up until its publication in 1923. See more about this work at The Royal Library