Ardour's processor box is the per-strip plugin chain where signal passes pre- or post-fader

In Ardour, ‘a processor is anything which treats the signal in some way and gets plugged into a mixer strip.’ The Processor Box is the visual list of processors on each track or bus. The fader always appears as a blue marker; processors above it (shown in red) run pre-fader; those below (green) run post-fader. Order matters: pre-fader effects like noise gates and compressors act on the unattenuated signal; post-fader effects like reverb sends respond to the final fader level. Processors can be dragged to reorder, toggled on/off by clicking their LED, and transferred between strips via drag-and-drop. A strip has no hard processor limit.

Examples

Insert a noise gate pre-fader on a vocal track so the gate sees full signal level. Place a reverb send post-fader so the wet/dry relationship follows the channel fader automatically.

Assessment

Explain the practical difference between inserting a compressor pre-fader versus post-fader on a drum track. Which position is more common and why?