The Amplifier section contains the Drive control that controls the level the 'tube amplifier' is operating on. This can be used to add tube distortion.
The Rotors sections controls the speaker's rotation speed. Tremolo is fast, Chorale is slow. Your MIDI keyboard's Modulation wheel can be used to switch speed if the Rotor is used in a Wheel Organ's effect slot. (Controller #1: 64 or higher is Tremolo, lower values correspond to Chorale.) The Stop button can be used to keep the rotors at a fixed position.
The Mics section controls the microphone placement used to record the speaker cabinet. Distance controls the distance between the mics and the cabinet. Spread controls the stereo channel separation. Balance controls the relative levels of the treble and the bass speakers. The cabinet is miked with two microphones at a 180 degree angle. This angle can be reduced to 90 degrees using the Narrow Angle button.