To a tone generation apparatus is removably attachable a plug-in board for generating a tone on the basis of performance information and extending the tone generating function of the tone generation apparatus. Tone color name information and tone color parameter name information of tone color data possessed by the attached plug-in board is stored in a nonvolatile memory. Thus, any tone color possessed by the plug-in board can be known with reference only to the nonvolatile memory and without a need to refer to the plug-in board. The nonvolatile memory can also store tone color data of a custom voice obtained by editing original tone color data of the plug-in board. With this arrangement, the plug-in board is allowed to obtain the tone color data of the custom voice from the nonvolatile memory, as necessary.