Special-type tone generators are capable of tone generation corresponding to rendition-style designating data, while ordinary-type tone generators are incapable of such tone generation corresponding to rendition-style designating data. When performance data for the ordinary-type tone generator are acquired in a case where the special-type tone generator can be used, presence of a predetermined rendition style is detected on the basis of various control data included in the performance data, the control data in a portion of the performance data, corresponding to the predetermined rendition style, is converted into simple data that does not represent the predetermined rendition style, and also rendition-style designating data specifying the predetermined rendition style is added. In this way, the acquired performance data are reformed into performance data for the special-type tone generator. Conversely, when performance data for the special-type tone generator are acquired in a case where the special-type tone generator can not be used, rendition-style designating data is deleted from the acquired performance data, and tone control data is added, in place of the rendition-style designating data, so as to achieve a desired rendition style. In this way, the acquired performance data are reformed into performance data for the ordinary-type tone generator.