Listener perception of musical expression in collaborative performance was explored in this study. Performances of two duos (a violinist and pianist, and a vocalist and pianist) were recorded. The level of expressivity of the violinist and vocalist remained stylistically appropriate during pieces; however, the pianist alternated between very expressive and unexpressive playing during each performance. The piece performed by each duo contained approximately equal sections of expressive and unexpressive playing by the pianist, and listeners heard each piece twice with the sections juxtaposed. Sixty-six undergraduate and graduate music students turned a Continuous Response Digital Interface dial to indicate their ongoing perception of expressivity as they listened throughout each performance. Graphic analysis of listeners' responses for both pieces illustrated that they differentiated between sections with expressive and unexpressive playing by the pianist. Statistical analysis revealed that sections in which the pianist played expressively were perceived with significantly higher levels of expressivity than unexpressive sections. We found no significant differences in perceived expressivity between performance experience groups, gender, graduates versus undergraduates, or orders. Thus, in collaborative performances of a vocalist or instrumentalist with a pianist, pianist expressiveness appears to influence perception of overall expressivity. (Contains 1 table and 2 figures.)