Any parameter associated with the circuitry that produces sound. For example, if a device uses looped digital waveforms to create sound, this controller may adjust the sample rate (ie, playback speed), for a "tuning" control. If a MultiTimbral device, then each Part usually has its own patch with its respective VCA, VCF, tuning, sound sources, etc, parameters that can be adjusted with this controller.
Note: There are other controllers for adjusting VCA attack and release times, VCF cutoff frequency, and other generic sound parameters.
0 to 127, with 0 being minimum setting.