The purpose of this study was to examine the effects of orchestration on musicians' and nonmusicians' (N = 40) perception of musical tension. Participants were asked to register their perceptions of tension using the Continuous Response Digital Interface dial while listening to three orchestrations (full orchestra, brass quintet, and solo piano) of the movement "Bydlo" from Mussorgsky's "Pictures at an Exhibition". The full orchestra and brass quintet stimuli were digitally altered to have the same amplitude, frequency, and duration as the orchestration for solo piano. Pearson product-moment correlations between the participant groups were statistically significant at the p less than 0.001 level and highest for brass quintet (r = 0.96), followed by full orchestra (r = 0.91), and piano (r = 0.78). Musicians perceived the piano orchestration as being the least tense of the stimuli while nonmusicians felt this was the most tense, perhaps suggesting a difference in perceived tension response based on timbre. (Contains 5 figures.)