Vibrato knob: Set the amount of vibrato (pitch modulation).
Semitones knob: Set the pitch of oscillator 2 in semitone steps, over a range of ±2 octaves.
Cents knob: Precisely adjust the frequency of oscillator 2 in cents (1 cent = 1/100 semitone).
Mix slider: Crossfade (set the level relationships) between the oscillators (Shape 1 and 2).
Download the guides:
Logic Pro User Guide: PDF