It would seem that the string quartet as a genre is not central to Nielsen’s oeuvre, at least if we consider the F major Quartet op. 44 as his only mature work for the medium. But this picture changes as soon as we count not merely his early apprentice works but also the three further quartets to which Nielsen himself assigned opus numbers and which he had published. After the early quartet studies, in which his familiarity with the classical repertoire may be seen, the following quartets – op. 13, op. 5 and op. 14 – show a progressive emancipation from tradition, which is particularly evident in their harmonic relationships. As the texture becomes far more complex, so the harmonic language achieves an increasing differentiation, going as far as bitonal passages in the E flat Quartet op. 14 (1897-98). The F major Quartet op. 44, composed in 1906, appears as a logical consequence, in that it unites the transparency of the early studies with the fluctuating tonality that thereafter becomes the basis for Nielsen’s output. From this perspective the string quartets acquire a central position, since they reflect his development more clearly than other genres. Moreover, they occupy a unique position when viewed not just against the background of Nielsen’s late works but in the context of the general history of the genre before 1900