“Mumblecore” was a cycle of independent, very low budget American movies, mainly shot on digital video, that emerged in the middle of the 2000s. The pejorative, jokey label, coined by a sound mixer, has since stuck. Yet despite mumblecore being named with reference to its sound, there has been little analysis, either academically or in the popular press, of its soundtracks, beyond dismissing the sound quality as “bad.” This article explores how mumblecore’s bad sound operates as a mark of its distinctive, perhaps excessive, indie-ness. It assesses the stylistic categorization of mumblecore, both academically and within the press, which provides context for audiovisual analysis of several mumblecore films, particularly emphasizing nonsemantic properties of mumblecore soundtracks. The aim is to unpack assumptions surrounding the role of the soundtrack and to ascertain what is meant when mumblecore is described as having “bad” sound—in other words, what puts the “mumble” into mumblecore.