There are two effects layers per source. This means that you can "stack" effects for a combination effect. In the same way you use the "Control To:" buttons to direct a slider/knob action to either A, B, or A&B, you use the "Effects To:" to direct the knob action to Layer 1 or Layer 2. Additionally, you can program a slider/knob to ignore the "Effects To:" setting using the "options" window, forcing the knob to always go to either Layer 1 or 2. It is worth noting that many effects have Brightness, Contrast, Saturation, and Hue controls built-in, so it may be redundant to stack the "BCSH" effect with some others. Finally, the effects Metrics (scale and rotate), 3DFlex, 3DShapes, and 3D.obj File are exceptions to the Layers. These are OpenGL effects, separate from the pixel-based effects of the other effects and have their own layer. Effect layers can be turned off individually using the buttons in the Effects interface, or all at once using the space bar or the "Effects off" button on-screen or on the controller.