Some virtual instrument and effects parameters just cry out for footpedal control—too bad you don't have a pedal that outputs MIDI data…or do you?
If you have a keyboard synthesizer or controller, it will probably have an expression pedal jack. The standard MIDI controller for expression is controller #11, and unless your keyboard or controller is really old, the odds are good that plugging an expression pedal into the pedal jack, then moving the pedal, will send controller #11 messages out the keyboard or controller's MIDI out. A floor multieffects for guitar that has a pedal may also transmit controller messages.
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