Which knob do you turn to adjust the complexity of the fills in Logic Pro?

The Fills knob is specifically designed to adjust the complexity of the fills in Logic Pro. This knob allows users to influence the intricacy and variation of the rhythmic patterns that are added during performance, thus enabling a more dynamic and rich musical expression. By increasing the complexity setting, musicians can introduce more elaborate variations in the fills, which can enhance the overall texture of their arrangements.

While the other knobs mentioned have distinct functions, they do not directly impact the complexity of fills. The Expression knob typically controls touch-sensitive dynamics, the Volume knob adjusts the level of sound output, and the Groove knob focuses on the timing and feel of rhythmic elements. Each of these plays a crucial role in music production, but for specifically adjusting the intricacy of fills, the Fills knob is the correct choice.