MIDI performance information is received via an operating system (OS) and an application-level software tone generator is driven on the basis of the received MIDI performance information, so as to allow the software tone generator to have an increased range of simple applications on the OS level. To this end, a fake driver is installed in the OS, and performance information output from application software is received by the fake driver via the operating system and then sent to the application-level software tone generator. As another example, the software tone generator is installed as a driver in the operating system so that information output from application software can be received by the software tone generator via the operating system.