One additional possible factor arises from evidence for the existence of frequency shift detectors (“FSDs”) in the auditory system (Demany and Ramos 2005), and that these FSDs may lead to the phenomenon of “frequency enhancement (FE)” (Erviti et al. 2011; Demany et al. 2013). Evidence for FSDs comes from a paradigm where, following an inharmonic complex tone, listeners are presented with a probe tone, which, in one task, can be slightly (typically one semitone) higher or lower than one of the components in the complex; subjects are required to report whether this shift is up or down. Demany and Ramos (2005) reported that performance in this task was better than in another task, where the probe tone frequency could equal that of one component in the complex (“present”) or fell mid-way between two components (“absent”). They attributed this to FSDs that were most sensitive to shifts of about one semitone (Demany et al. 2009) and concluded that subjects could hear a shift in the pitch of a component that was not heard in the complex and was not heard retrospectively when the probe was presented. In our test trials, one of the harmonics (third or fourth) differed slightly between the first and second intervals, and so this shift may have been detected by an FSD. Subsequently, Erviti et al. (2011) argued that detection of shifts via FSDs could lead to FE, as demonstrated in an experiment where a “test” complex was preceded by a precursor that was identical to the test complex or differed from it (only) in a one-semitone shift in one of its components. A probe tone, presented after the test, had a frequency equal to the possibly shifted component or mid-way between two adjacent components, and subjects reported whether the probe was present in the test complex. Erviti et al. (2011) reported that performance was better when the frequency shift was present rather than absent and concluded that the frequency shift “enhanced” the auditory representation of that component in the test complex, thereby improving performance on the present/absent task. This is relevant to our paradigm because if this improved performance reflects increased segregation of that component, then segregation of the mistuned component in the second interval of our test trials may have been increased by the complex presented in the first interval. This in turn may have allowed subjects to “hear out” the mistuned component with smaller mistunings than in the Moore et al. (1986) study, where the mistuned harmonic complex was not preceded by a harmonic precursor.