Theophrastus frag. 716 [Fortenbaugh] attacks the thesis that differences between musical pitches are quantitative. Most of its fire-power is directed at harmonic theory in the 'mathematical' or 'Pythagorean' style, but one short passage (lines 108 ff.) is not. Previous commentators have identified its target as Aristoxenus; but I argue that Theophrastus' account does not fit Aristoxenus' position, and that we should look for his target in the work of earlier 'empirical' theorists. After reviewing and rejecting various possibilities, I tentatively suggest that Theophrastus' conception of the empiricists' standpoint may originate i