Two experiments investigated the behavioral and electrophysiological effects on human auditory selection of the psychophysical discriminability of a distractor channel in memory. Participants performed a set of baseline (single distractor) and filtering (multiple distractors) tasks, classifying the pitch of targets, while ignoring pitch variation in temporally distinct distractors, which differed from targets in timbre (Experiment 1) or loudness (Experiment 2). Increased distractor change progressively disrupted target accuracy and reaction time, and fostered confusion in distinguishing target from distractor channels. Physiologically, relative discriminability only affected distractor waveforms, whether or not distractor values physically differed across tasks, enhancing the N1 response while reducing an inhibitory slow-wave component. The results suggest that inhibition fails as distractors activate a wider range of the task-relevant continuum in working memory.