Research on listeners' perceived emotions in music draws on humanand synthetic stimuli. Although research has shown that realistic synthetic audio can convey emotions, studies that compare listeners' experience of synthetic audio and human performances are limited. Using short musical excerpts, we investigate the effect of performance (human vs. synthetic) and instrumentation (piano vs. string quartet) as well as the influence of twelve musical features on participants' ratings of five emotional dimensions (mood, energy, movement, dissonance, and tension). Findings show a small main effect of performance and a large main effect of instrumentation. Synthetic audio was perceived as more positive in mood and less tense than human performances. Piano excerpts were also perceived as more positive and as conveying less tension and energy than synthetic excerpts. Several rhythmic and pitch measures were reliably predictive of participants' perceived emotions, supporting the need for considering finer-grain structural features when using naturalistic stimuli.