 Though jazz is not necessarily improvisational, and very few jazz performances lack any sort of prior compositional process, the centrality of improvisation to jazz presents a challenge to the musical ontologist. One might argue that jazz works are ontologically like classical works—composed for multiple, different performances—but that they tend to be thinner, leaving more room for improvisation (Gould &amp; Keaton 2000; Young &amp; Matheson 2000). The difficulty is to specify the work without conflating one work with another, since tokening the melody is not required, and many works share the same harmonic structure. As a result, some argue that the performance is itself the work (Alperson 1984; Hagberg 2002; S. Davies 2001: 16–19). One problem here is parity with classical music. If jazz performances are musical works in their own right, it is difficult to deny that status to classical performances of works. This seems to multiply works beyond what we usually think is necessary. A third possibility is that in jazz there are no works, only performances (Brown 1996, 2000: 115; Kania 2011b). This is counterintuitive if “work” is an evaluative term, but it is not obvious that this is the case.