In music ontology, ‘pure’ formalists regard musical works as ‘colourless’ sound structures. One alternative, known as timbral sonicism, accepts that a musical work's orchestral colour is a factor in its identity, but denies that the use of the specified instruments is required for an authentic rendition of the work provided that sounds as of those instruments are achieved. This position has been defended by Julian Dodd. In arguing against his view, I appeal to empirical work showing that composers, musicians, and listeners typically hear through music to the actions that go into its production. In this respect, musical listening reflects the standard account of ‘ecological hearing’; we appreciate sounds as providing information about their sources rather than for their intrinsic qualities. On this basis, I suggest that musical instruments are not merely means to the production of the sounds of performances. Their use is mandated if such performances are to be properly formed. More specifically, when composers are able to make the instrumentation of their compositions central to the identity of those compositions, accurate performances must involve the appropriate use of the specified instruments.