The purpose of this study was to investigate the ability of trained musicians and musically untrained college students to discriminate music instrument timbre as a function of duration. Specific factors investigated were the thresholds for timbre discrimination as a function of duration, musical ensemble participation as training, and the relative discrimination abilities of vocalists and instrumentalists. Under the conditions of this study, it can be concluded that the threshold for timbre discrimination as a function of duration is at or below 20 ms. Even though trained musicians tended to discriminate timbre better than musically untrained college students, musicians cannot discriminate timbre significantly better then those subjects who have not participated in musical ensembles. Additionally, instrumentalists tended to discriminate timbre better than vocalists, but the discrimination is not significantly different. Recommendations for further research include suggestions for a timbre discrimination measurement tool that takes into consideration the multidimensionality of timbre and the relationship of timbre discrimination to timbre source, duration, pitch, and loudness.