Midi Sustain Pedal in Garageband 10.2.0

I have a Korg SV-1 keyboard, which also acts as a MIDI controller. I just figured out today that I can connect my Korg keyboard to my mac and play sounds in Garageband using keys on my keyboard, which I have been using to play some of the organ sounds that come with Garageband, specifically the Vintage B3 organ. When I depress the sustain pedal connected to my keyboard, instead of holding out the notes, it increases the speed of the rotor cabinet, which I do not want. Is there a way I can change this without having to pay for Logic Pro X or Mainstage?