Pipe-Organ Combination Actions: Pistons, Capture, Setterboards, and Memory Levels

A combination action is three functions working together, and none of them alone is the combination action. The Cinema Organ Society’s Theatre Organ Fact Finder decomposes it into a combination memory that holds the registrations, a signaling means, the pistons, which it describes as effectively electric switches, and a stop action that physically drives the stops on or off. The piston is therefore a signal rather than a store: pressing it asks the memory for a combination, and the stop action carries that combination out on the drawknobs or tabs.

Solid State Organ Systems’ operation guide for its MUCAP multilevel capture system states the same division of labor from the memory side, where a memory level is a complete set of piston memories and the pistons recall whatever the selected level holds for them. That is why the same piston can produce a different registration on a different level, and why what a piston does is a property of the memory it points at rather than of the button itself.

Combination pistons are found only on organs with electric stop action, in the Organ Historical Society’s account of keyboards and consoles, because a piston can only recall a registration if something other than the organist’s hand moves the stops. That is the stop-action part of the three-part definition at work. Registration aids on instruments without electric stop action, from composition pedals to a purely mechanical combination action, are described at the end of this page.

A general piston affects stops across the console while a divisional piston affects only the stops of one division, and the difference is one of scope rather than of mechanism. Peterson’s ICS-4000 user manual puts it as general pistons affecting virtually all the tabs on the console and divisional pistons affecting only the tabs in a particular division; the word virtually is Peterson’s own hedge, and the same manual documents a piston compass function that can narrow what any individual piston controls. Peterson’s organist leaflet for its solid-state combination action adds that pistons are arranged by the organ builder as divisional or general, which is why one product can appear with different piston layouts on different consoles.

On a typical American console the divisional pistons sit centered under their own manual, the general pistons sit to the left under at least two of the manuals, and miscellaneous pistons such as reversibles sit to the right, as Brigham Young University’s OrganTutor describes the usual zoning of the keyslip so that an organist can find controls by feel. It is a usual pattern rather than a rule, and the number of pistons varies widely between consoles.

A toe stud is functionally a thumb piston for the feet, and pedal divisional pistons often appear only as toe studs above the pedalboard, so a console without pedal divisional thumb pistons has not necessarily gone without pedal divisionals; OrganTutor and the Wicks Organs glossary both describe the equivalence.

A cancel is a scoped clearing control, not a stored registration. Peterson’s ICS-4000 manual describes a General Cancel or Divisional Cancel piston as turning off all of the associated tabs, and a Diapason report on Scott Smith Pipe Organs’ re-creation of Skinner Opus 751 documents divisional cancels provided within each divisional piston group. A cancel empties its range and a piston fills it.

On a programmable control system the engraving on a piston records what the builder intended, not what the piston is limited to doing. Opus-Two’s organist manual states that a piston labeled general or divisional is not thereby limited to that capacity, because each piston can be ranged to control one division, several divisions, all divisions, or particular features. Peterson’s ICS-4000 manual provides a piston compass function that lets an organist restrict an individual piston so that it manages only the stops chosen for inclusion, and places that function in an organist-accessible menu rather than a supervisor-only one. Each statement speaks for its own product, but together they explain why two consoles with identical engraving can behave differently: the set of stops a piston governs is a configured property of the control system.

Whether the organist, the builder, or a technician is the right person to change that property on a particular instrument is a question of access rather than of mechanism, and it belongs on the page on configuration software, firmware, and technician access boundaries.

In the capture method the organist registers the stops first, then holds Set and momentarily presses the piston that should remember them. Peterson’s ICS-4000 manual documents that gesture as its Capture Method, and Solid State Organ Systems’ MUCAP operation guide describes the same conventional procedure for a solid-state capture system: select the stops, hold SET, press the piston, release both, with an on-screen or indicator confirmation. Brigham Young University’s OrganTutor teaches it as the standard procedure on most organs with a standard combination action that is not locked; a locked or password-protected action will not respond to the gesture, and that is a designed condition rather than a fault.

The word capture also names a memory family, so this page uses capture method for the setting gesture and capture system for the memory type. The Theatre Organ Fact Finder describes an electro-mechanical setter that captures by holding a setter piston and then pressing the target piston, with an electrical contact for each stopkey that is on latching onto a conductive rail dedicated to that piston, and the solid-state systems above call themselves capture systems in the same sense.

In the tripper method the organist holds the piston first and registers the stops while holding it. Peterson’s ICS-4000 manual documents it beside the Capture Method as a second available procedure, and Peterson’s name Duo-Set denotes a combination action in which both tripper and capture setting may be used, though the name alone does not say that every installation is wired for both. Holding the piston while selecting the stops is also the first of the three setting methods the Organ Historical Society records.

Timed variants exist under other labels. Peterson’s organist leaflet for its solid-state combination action describes a tripper mode in which the system enters set mode automatically once a piston has been held for about one second, and Solid State Organ Systems’ MUCAP guide notes that some systems provide an autoset in which holding the piston alone for about a second performs the capture.

Both methods are documented as selectable on one modern system. On older instruments the hardware determines which method exists, and the gesture an organist remembers from one console may simply do nothing on another.

The third way to set a combination is not at the keyslip at all but at a setter board, where a switch for each stop under each piston holds the stored state. The Organ Historical Society records three methods by which adjustable combinations have been set: holding the piston while selecting the stops, using a separate setter piston, or operating switches on a setter board. A 1980 capture patent describes the setter board it sought to displace as a row of switches provided for each divisional piston, the memory being set by moving those switches to the desired on or off positions, and notes that proper operation required a large number of such switches.

A setterboard is a matrix of switches with stops on one axis and pistons on the other, and it is the memory of the combination action rather than part of the control system’s circuitry. John Bishop describes a 1956 Holtkamp combination action with a setterboard carrying rows of toggle switches, the stops on one axis and the numbered pistons on the other, and elsewhere describes setter board systems as hundreds of toggle switches in rows, pistons running left to right and stops up and down. The Theatre Organ Fact Finder gives the same picture as a matrix array of switches per department, rows for pistons and columns for stops. Setterboards were built by many firms in varying forms.

Where it lives depends on the size of the instrument. The Fact Finder places the setter board in the back of the console or behind the kneeboard on smaller organs, with massive setter boards in a separate room on large instruments, and notes that the arrangement needs supplementary multi-contact relays near the board, one per piston with as many contacts as there are stops controlled. A practitioner account on the Organ Forum describes mechanical setterboards housed in a drawer on each side of the console, one toggle switch per stop for every piston, with the stops identified on labeled tabs and no electronic components at all; that account is uncorroborated by a manufacturer document and names no builder or date.

A setter-board combination action is a discrete, removable assembly. A 2017 Milnar Organ Company sales list offered a stop rail with a fully wired setter board combination action, listed separately from a relay for one 61-note division, which shows that the item circulates as an identifiable part without saying anything about how common it is or naming a maker.

A setter board can leave a stop alone when a piston is pressed, and an electro-mechanical capture normally cannot. The Fact Finder’s setter board entry states that each switch has three positions, on, off, and neutral, the neutral setting leaving the stop unaltered when the piston is pressed, which the source notes is particularly useful for tremulants. Its electro-mechanical setter entry states that those systems normally had no facility for a neutral setting, although individual stops could be neutralized by the organ builder, and that a capture records the complete on-or-off state of every stop in its range at the moment of capture. The difference is functional, not merely technological: a setter board offers a neutral choice per stop, and an electro-mechanical capture records everything in range.

On one modern system the exclusion is configured rather than switched. Peterson’s ICS-4000 piston compass function restricts an individual piston so that it manages only the stops chosen for inclusion, and a stop left out of a piston’s compass is left alone by that piston; that speaks for Peterson’s product only.

A memory level is a complete and independent set of piston memories, so changing level changes what every piston recalls without altering anything stored on any other level. That definition comes from Solid State Organ Systems’ operation guide for its MUCAP multilevel capture system and serves here as a worked example of the term. Brigham Young University’s OrganTutor gives the multiplying arithmetic: an organ with ten general pistons and eight memory levels can hold eighty distinct general registrations. The arithmetic is the source’s illustration; the actual capacity of a console depends on how many pistons and levels its system provides and on whether levels are grouped into folders.

Divisional and general pistons need not share a level. The MUCAP guide states that where a capture system provides independent selection of divisional and general memories, each memory level of divisional and of general pistons may be locked independently, a conditional feature of the system and of the particular installation rather than a universal one. Peterson’s organist leaflet for its solid-state combination action described the same idea from the organist’s side: selecting a different level with a switch allows entirely different registrations on the same pistons.

Documented memory-level provisions differ by an order of magnitude between systems, and no figure is a standard. Syndyne’s 2006 manual for the CS5608 combination action offered up to 64 levels with a standard twelve-level rotary selector. Solid State Organ Systems’ CFM page offers 40, 100, 300, or 1,000 levels or a Library system. Peterson’s ICS-4000 product page offers a standard 100 levels, optionally upgradable to 256 and grouped into organist folders. Opus-Two’s 2021 organist manual documents a 10,000-level action divided into folders of 300 levels each. Each figure speaks only for the named product and generation as its own document describes it; the numbers are capacities offered, not counts enabled on any particular console, and the 2006 figure says nothing about current products.

The number of levels is a generation marker rather than a property of the technology. Solid State Organ Systems’ own account of its legacy capture systems runs from a first solid-state capture system of the early 1970s with one memory level, through a two-level version that stayed in production until 1993, to an eight-level system introduced in 1984, and states that virtually unlimited amounts are now possible. Those dates are that company’s; they cannot be transferred to other makers’ systems or used to date an unidentified capture system from its level count alone.

A sequencer lets the organist program an ordered series of registrations and step through them with Up and Down or Next and Previous controls, so that one repeated gesture replaces finding a different piston for each change. That description comes from a 2016 Classic Organ Works article written by a control-system supplier about sequencer designs including its own; the article states that all of its systems have Up and Down pistons active when a Sequencer piston is engaged.

The gesture belongs to an older tradition than the electronics. A research report from Lulea University of Technology identifies two established combination-system traditions: a sequential method common in continental Europe, in which the performer steps through consecutive combinations to retrieve the next setting, and a fixed-piston method associated with the Anglican tradition, using a fixed number of programmable general and divisional pistons, with combinations of the two existing in modern systems.

Recording and playing back a performance is a separate job from stepping through registrations, and it is covered on the page on how pipe-organ MIDI systems work.

Classic Organ Works distinguishes three sequencer designs, and the design decides what an organist can edit later. A registration sequencer allows steps to be inserted, deleted, or modified without reprogramming subsequent steps. A general piston sequencer is tied to the general pistons and so cannot insert or delete a registration between two existing steps. An any-piston sequencer allows piston presses to be repeated and steps to be deleted and re-added without disrupting sequence order. This is one supplier’s taxonomy; other manufacturers use different names, and Peterson’s ICS-4000 product page documents comparable designs under the labels American and European sequencer.

Opus-Two’s 2021 organist manual documents a piston sequencer that steps through the existing general pistons rather than a separate store of registrations and automatically advances to the next memory level when the last piston is reached, which is how a general-piston design chains levels together to extend a sequence. That speaks only for Opus-Two’s product.

In a piston sequencer it is the piston press that is stored, not what the piston does, so if a piston’s registration is later changed the sequencer will bring on that piston’s new contents. Classic Organ Works states this as a warning. It applies to piston-based sequencers; a sequencer that stores registrations directly rather than piston references does not have the dependency. The practical consequence is that an organist who edits a general piston between rehearsal and service on a piston-based sequencer has also edited every step that points to it.

Combination actions predate electronics, and an older instrument’s registration aids belong in the same account. John Bishop records that E. and G. G. Hook Opus 283 of 1860 had iron pedals for Piano and Forte combinations on both the Great and the Swell, and the 1903 restatement of the Royal College of Organists’ recommendations required composition pedals to be double acting and self-recovering; the Hook example is one instrument reported by a named practitioner, and the recommendation is a proposal rather than evidence of what builders did.

A combination action can be purely mechanical. Austin Organ Company’s 1913 patent describes a design in which the organist depresses the wanted stop keys and pushes a piston, whose horizontal movement of a trace shifts pivoted actuators into positions that thereafter move those stop rollers whenever that piston is used. A second Austin patent of the same year stores combinations outside the stop action altogether, as rows of perforations in a removable insulating sheet carried on a conducting table, advanced one step at a time by an electromagnet-driven pawl and rack so that spring contact fingers projecting through the perforations close the circuits of the stop magnets. Each patent establishes a claimed design, not that Austin fitted it to any particular instrument or to instruments generally.

Bishop also states that Skinner began making remote combination actions around 1912, describes them as electro-pneumatic mechanical binary computers, and names Saint Thomas Church in New York City as having one of the earliest; the date, the earliest-example claim, and the binary-computer description are his rather than contemporary terms.

The label on a piston will not say which of these mechanisms sits behind it, or what condition that mechanism is in. Both are established at the instrument, and both shape what repairing, replacing, or extending a combination action would involve.