Mackie Control: Modifier Buttons
The four Modifier buttons correspond to the modifier keys on your computer keyboard (but function independently from them). You can use these buttons, along with the appropriate key on your computer keyboard (or with the mouse), in place of using the corresponding modifier key. This also applies to modified Mackie Control commands.
A generic description of each button follows:
SHIFT: Provides an alternate function or meaning for a button.
OPTION: The function applies to all channel strips. For relative value changes, sets the value to its minimum, default, or maximum, depending on whether you’re increasing or decreasing it.
CONTROL: While held down, the group clutch is engaged, and channel strip groups are temporarily disabled.
CMD/ALT: Allows fine-tuning, or another variation, of the function.