A ‘processor’ is a thing which treats the signal in some way. Ardour provides several builtin processors, such as the "fader" processor which controls the gain (volume) of a track or bus. Processors can also be plugins used for effects or as instruments, as well as sends/inserts which are used to change signal routing. The arrangement of processors is arbitrary, and there is no limit to how many there can be.
The main box in the top half of a mixer strip shows the processor list. Processors are shown as coloured rectangles, with a small ‘LED’ beside them; this indicates whether or not the plugin is enabled, and can be clicked to enable or disable a processor. The colour of the processor depends on its location in the sequence; processors that occur before the fader are coloured in red, and those after are coloured green (in the default theme).
The processor box will always contain a blue processor called ‘Fader’. This indicates where in the processor chain the main volume fader is located — this is the fader shown in the lower half of the strip.
Processors can be re-ordered using drag-and-drop. Dragging a processor allows it to be moved around within the chain, or copied to another processor list on another track or bus.
To the left of the name of each processor is a small LED symbol; if this is lit-up, the processor is active. Clicking on it will deactivate the processor. It will still pass audio or MIDI signals, but they will not be affected.
Finally, processors can be added to or removed from the chain. Right-clicking the processor list does three things:
From the menu, some new processors can be inserted.
Context-click on the processor you want to remove.