Control

Expression pedals and MIDI controllers carry control information rather than audio signal: an expression pedal sends a continuously variable control voltage a host pedal reads to sweep one of its own parameters underfoot, and a MIDI controller sends discrete messages — a patch change, a tap-tempo pulse, an on/off toggle — to whatever pedal or pedals are listening for them.

The types in this family

• Expression pedal (rank — not in the chain): An expression pedal carries a control voltage, not audio; it plugs into the pedal it controls and is nowhere in the signal path.
• MIDI controller (rank — not in the chain): A MIDI controller sends messages, not audio; it plugs into the pedals it controls and is nowhere in the signal path.

Where it sits in the chain, and why

Neither type is a link in the audio signal path at all, which is why neither one occupies a position in the chain the way an audio-processing pedal does. An expression pedal plugs into the specific pedal it controls and sits wherever is convenient underfoot rather than at a defined point in the signal flow; a MIDI controller connects to whatever pedals on the board accept MIDI messages, often over a shared cable running to several pedals at once. A control pedal on a board with nothing that accepts its input has, quite literally, nothing to plug into — exactly the situation the chain planner’s own expression-has-no-host and midi-has-no-host warnings exist to catch.

Power notes

An expression pedal is typically a simple passive potentiometer with no power requirement of its own — it draws whatever small amount the host pedal’s own expression circuitry provides. A dedicated MIDI controller is an active digital device and needs its own power, usually a modest draw comparable to a buffer or a simple digital pedal, though a controller built around a larger screen or more elaborate switching can draw more.

General guidance for the family, never a specification for any individual pedal — always confirm voltage, polarity, current draw and isolation from the maker’s own documentation before wiring a real board.

Every rank and reason above is quoted straight from pedal-chain-planner.js's PEDAL_TYPES — the same taxonomy this site's chain planner runs and docs/gearwarrior-pedals-contract.md documents. No second table.