Listeners were tested on their ability to discriminate "standard" and "comparison" pure-tone musical intervals that differed in size by 20 cents (1/ 5 of an equal-tempered semitone). Some of the intervals were prototypic, equal-tempered perfect fifths (exactly 7 semitones, or 700 cents). Others were mistuned to various degrees (660, 680, 720, or 740 cents). The intervals were melodic (sequential) in Experiments 1 and 2 and harmonic (simultaneous) in Experiment 3. Performance was neither enhanced nor impaired in comparisons that included the prototype. In other words, no "perceptual magnet" or "perceptual anchor" effects were observed. Nonetheless, performance was markedly asymmetric. Regardless of listeners' musical expertise, discrimination was superior when the standard interval was more accurately tuned than the comparison interval (e.g., 700- cent standard, 680-cent comparison), compared with when the comparison was more accurately tuned than the standard (e.g., 680-cent standard, 700-cent comparison).