This paper addresses the following problem: to what extent do ontological considerations about musical works affect our evaluation of performances of those works? I argue for the claim that at least some important grounds on which performances are evaluated are specific to them, in that these grounds are either independent from, or related but not fully determined by, the properties of the works they are of. In the first part of the paper, I explore the relations between good-making features of works and of performances of them. The second and third parts develop two kinds of example in favour of the claim above. In the last part, I discuss the significance of those examples in relation to the ways in which performances are assessed, and explore some further ramifications of them.