We combine perceptual research and acoustic analysis to probe the messy, pluralistic world of musical semantics, focusing on sound mass music. Composers and scholars describe sound mass with many semantic associations. We designed an experiment to evaluate to what extent these associations are experienced by other listeners. Thirty-eight participants heard 40 excerpts of sound mass music and related contemporary genres and rated them along batteries of semantic scales. Participants also described their rating strategies for some categories. A combination of qualitative stimulus analyses, Cronbach’s alpha tests, and principal component analyses suggest that cross-domain mappings between semantic categories and musical properties are statistically coherent between participants, implying non-arbitrary relations. Some aspects of participants’ descriptions of their rating strategies appear to be reflected in their numerical ratings. We sought quantitative bases for these associations in the acoustic signals. After attempts to correlate semantic ratings with classical audio descriptors failed, we pursued a neuromimetic representation called spectrotemporal modulations (STMs), which explains much more of the variance in semantic ratings. This result suggests that semantic interpretations of music may involve qualities or attributes that are objectively present in the music, since computer simulation can use sound signals to partially reconstruct human semantic ratings.