Pain and Dissonance

Because Nietzsche's evaluation of Pain as potentially positive seems to oppose those of both Spinoza and Schopenhauer, two of his primary influences, merely dismissing the significance of it as "secondary", as he does in Beyond Good and Evil #225, without supplying a methodical derivation of that characterization, is insufficient.  However, that opposition entails either that Pain is not a sign of weakening or that weakening is not 'bad', neither of which seems easily demonstrable in terms of the Will to Power, which is constituted by relations of strength.  Instead, an alternative ground is suggested by his perhaps earliest consideration of Pain, appearing prior to his introduction of the Will to Power--in Birth of Tragedy #24, where he characterizes Dissonance as "primordial joy experienced even in pain", and as "disharmonic".  Implicit in these representations is a concept of Phenomena as constituted by a range of degrees of harmoniousness, with Pain and Joy at the extremes, and Dissonance their midpoint.  On that model Pain and Pleasure are not atomistic, mutually exclusive moments, so, nor are the various experiences of suffering that he judges as having potentially positive value.  However, it is unclear if such nuance is representable in terms of the Will to Power.