Among other things, this software allows one to change the USB audio input type. This provides a workaround for a problem in OS 9 with the Apple USB audio drivers. Normally a USB audio input device would "register" itself as a Microphone Input so the PowerWave is compatible with more audio applications.
However in order to use the playthrough feature in the Sound control panel in Mac OS 9, the device type must be Line Input. This PowerWave Control allows this selection, in addition to other features.