A group of 40 monolingual Spanish-speaking subjects, aged 19-35, participated in a discrimination perceptual test in which the subjects listened to two stimuli and they had to answer whether both belonged to the same speaker or to different speakers. Stimuli consisted of 24 pairs of utterances, 24 pairs of words and 24 pairs of syllables. The participants were 20 female and 20 male speakers. Within each gender group, half of the participants were trained in a musical instrument and half of them were not. None of the subjects knew the three brothers whose voices were used to create the test stimuli. The results suggest that two of the three variables considered in this study (namely, stimulus duration and musical training) are significant to discriminate voices while the listener’s gender is not significant. These results may be useful for Forensic Phonetics.