Harmony and Dissonance

In section 2 of Birth of Tragedy, Nietzsche includes in the "essence" of Dionysian music, "the utterly incomparable world of harmony".  But that characterization leaves the relation between Music and Tragedy unclear, until, in section 24, he introduces "dissonance" as the musical expression of the "ugly and disharmonic", and as the musical ground of Tragedy, though without further explaining the apparent contradiction between Harmony and Dissonance.  One, and perhaps the only, way to reconcile those two is to conceive Harmony as not a precise condition, but as comprising a range of degrees of togetherness among a multiplicity of components.  On that basis, Dissonance consists in maximum degrees of disassociation within that range.  Similarly, the condition of Nature that it expresses is not absolute separation, but relative disassociation.