Pipe-Organ Stop Controls: Drawknobs, Tabs, and Rockers

In modern usage a stop is a device that selects the rank or ranks from which pipes will sound whenever a key is played, and the stop control is the console end of that device. This is a definition about control, not about tone: it says which ranks answer the key, and nothing about what those ranks sound like, which is a separate matter.

Consoles present these controls in several common physical forms. Stop knobs, also called drawknobs, are set into stop jambs beside the manuals; tablet- and rocker-style controls are usually carried on a stop rail above the highest manual. The terminology overlaps among builders, and a single console may combine a jamb of drawknobs with a rail of tabs. Whichever form is used, the physical control says nothing about the stop action that carries out its request.

The word stop is placed differently by different authorities. The American Guild of Organists glossary defines a stop as the knob or tablet that pulls a rank of pipes into play, which locates the word on the control. The Organ Historical Society glossary defines a stop as one or more ranks of pipes of consistent tonal design activated by a single control from the console, which locates the word on the pipework and treats the control as the activator. One builder’s glossary, from the Wicks Organ Company, defines a stop as an individual voice composed of one or more ranks whose name carries a pitch number such as 16 or 4; that is what one company says, and other builders and reference works define the term differently. These senses coexist, and they are not interchangeable when stops are being counted.

The counting consequence runs in both directions. A single stop control may govern several ranks, as with a Mixture IV or a Cornet V, so a published stop count does not by itself state how many ranks or pipes an organ contains; it is the rank count that relates directly to pipe count. In the other direction, unification uses one rank of pipes to play at more than one pitch or on more than one keyboard, and each stop control providing that facility is called a unified stop, so one rank can generate several stops. On this page, stop control means the device on the console and rank means the pipes it governs.

A drawknob is a stop control descended from the original mechanical type, in which a knob on the end of a shaft was pulled to turn the stop on and pushed to turn it off. That is a builder’s glossary definition, and it describes the gesture rather than the mechanism: the pull-and-push survives on electric-action consoles where the knob no longer moves any mechanical trace. The drawknob is one of the three physical families of stop control, and it may share a console with tabs of either other family.

On larger consoles drawknobs are commonly installed in two stop jambs, one to the right and one to the left of the manuals, angled inward toward the organist for ease of access. Terraced, drop-sill, and English drawknob jambs are documented variants of that arrangement. One builder describes its own drawknob range as the traditional drawknob with or without a drop sill, the English drawknob, a low-profile terraced form, and backlit drawknobs; that is a description of one firm’s range, not a measure of how common each form is.

A tilting tablet is a rocker switch in the console for turning on stops or couplers, on when pushed in at the bottom and off when pushed in at the top. Those on and off directions are a convention rather than a rule: on an unfamiliar console they should be confirmed rather than assumed. Tilting tablet, stop tab, and rocker tab are overlapping terms rather than universally fixed categories. Here, tilting tablet means a tablet-style control that rocks between positions; builders may call related forms stop tabs or rocker tabs. These controls are usually carried on a rail rather than on a jamb.

The tablet and the part that moves it are separate items. A 2006 trade catalog listed tilting tablets in four styles, in widths from roughly five eighths to thirteen sixteenths of an inch and lengths from two to two and three eighths inches, together with a tilting tablet magnet assembly available for manual or electric operation; that establishes what was offered to builders in 2006, not what is available now or what any particular instrument contains. The actuator that sits behind a moving tilting tablet or stop key is a stop action magnet, usually abbreviated SAM, and it is the piece that a combination action drives when it repositions the tablet. One builder lists stop tablets, rocker tablets, and backlit rocker tablets among the styles it builds.

On two-manual consoles stop tabs are usually carried on a stop rail just above the highest manual, in the position occupied by the coupler rail on larger consoles. On a large drawknob console that same rail position is occupied by couplers rather than speaking stops, so the contents of a rail cannot be assumed from its position; a rail above the top manual may be the whole stop list or may be couplers only.

Theater pipe-organ consoles present their stop controls differently, as tabs of plastic, originally celluloid, spaced around a horseshoe-shaped console, with a double bolster denoting two rows of tabs around the horseshoe. That is theater-organ practice; church and concert consoles of the same period generally used jambs or a stop rail rather than a horseshoe.

The general principle is that stop controls are arranged by division, and within a division by family, pitch, and loudness. The Organ Historical Society, writing in 1998, describes drawknobs arranged by division with flues below reeds, lower pitches below higher pitches, and louder stops below softer stops, and states that tilting tablets and stop keys follow the same ordering principle but read left to right rather than top to bottom. This is described as a general principle; individual builders document different orderings.

The AGO Standard Console Specifications recommend an order by pitch and family: 16-foot flues, 8-foot flues, 4-foot flues, 2-foot flues, mixtures, then 16-foot reeds, 8-foot reeds, and 4-foot reeds, arranged loudest to softest within each pitch group. This is a voluntary recommendation about the arrangement of controls, not a statement about which stops an instrument contains, and builders document other ordering conventions alongside it.

Which division goes on which jamb, and where the break falls within it, is decided by the builder rather than fixed by any rule. One firm describes its three-manual terraced console with the Swell on top and the Pedal below on the left terraces, and the Great and the Choir or Positif on the right terraces, with care taken to make a logical break, preferably with the flues to the left and the reeds to the right. That flues-left and reeds-right break contrasts with the vertical flues-below-reeds ordering the Organ Historical Society describes, and neither is a fixed rule: jamb layout is a builder decision, not a fixed standard.

A layout can establish which division a control belongs to and, once you know the convention in use, where a control of a given family and pitch will sit within its group. It cannot establish what a rail contains, since the same rail position holds speaking stops on a small console and couplers on a large one, and it cannot establish the stop action behind the controls, since the physical form of a stop control says nothing about the action that carries out its request. Which manual plays which division, and how the pedalboard relates to its own division, is explained on Pipe-Organ Manuals, Pedalboards, and Divisions Explained.

On a modern electric-action console a visible control sends a request that a separate switching system executes, so the behavior of a piston, a coupler tab, or a shoe is determined by how the system is configured and not by the control itself. That principle is drawn from what control-system manufacturers say about their own equipment: that the console’s keys, stops, and expressions are read and routed to a processor that drives the windchests; that coupling is processed in the control computer rather than by coupler relays; and that a piston’s scope is a configurable property independent of its engraved label. The principle does not apply to mechanical stop and key action, where the control and the implementation are one linkage. What the switching system does at the windchest is outside this page.

A stop control therefore does up to three separable jobs. It requests a state when the organist moves it; it displays a state, by its position or by a light, so that the organist can read the registration; and something else, the stop action or the switching system, implements the state at the pipes. In the original mechanical drawknob the shaft the organist pulled was both the request and the linkage. On an electric-action console the jobs are separated, and the form of the control tells you nothing about which switching system sits behind it.

A control that moves displays its state by where it sits, and on an electric-action console that position is not held by any mechanical trace running to the pipes. One control-system manufacturer describes its solenoid drawknob as gliding in and out manually as well as automatically, driven by four stationary electromagnetic coils, which makes it a moving stop control that the combination action can reposition; that is the company’s account of its own product, not an independent measurement. Behind a moving tilting tablet or stop key the equivalent part is the stop action magnet. Where a control is driven that way, a piston that recalls a combination moves it so that the visible position matches the state the combination action has just set. How pistons, memory levels, and the combination action itself divide the work is covered on Console and Control Systems.

A control does not have to move to request a state. A 1980 Baldwin patent describes stop tabs that are momentary-acting and do not move under combination control, with a microprocessor scanning the tabs and storing and recalling stop states in random-access memory, and it criticizes the earlier approach of moving stop tabs with solenoids as consuming tens of watts to control milliwatts of stop power. That patent was drawn for electronic organs; it establishes a claimed design and the applicant’s critique of prior art, not pipe-organ field practice or adoption.

Where a control does not move, its state has to be displayed some other way. One control-system manufacturer offers a lighted pushbutton as a way to add stops, tabs, and couplers to consoles where space is limited, and a lighted rocker tab board described as cost-effective stop controls with a positive tactile action; another builder lists backlit drawknobs, backlit rocker tablets, and touch-screen stop control among the styles it builds. The practical difference is that an illuminated pushbutton indicates state by light rather than by position, so a photograph of such a console cannot be read for stop state the way a drawknob jamb can. The expression shoes, the crescendo pedal, tutti, and reversibles are separate controls with their own page: Expression Shoes, Crescendo Pedals, Tutti, and Reversibles.

The stop controls on a console may be far younger than the console around them. Console rebuild services advertised by builders include fitting new stop tabs or drawknobs, replacing a large older mechanical combination action with a new one, adding combination memory levels, fitting new pistons and new keys, evaluating and retaining the existing keyboards and pedalboard where desirable, and installing new contacts on the expression and crescendo shoes. Two firms describe those services; the descriptions establish that the operations are routinely available, not that any given console has had them.

Because rebuilding routinely replaces the stop controls, pistons, shoe contacts, and combination action while retaining the shell, keyboards, and pedalboard, the age of a console shell is not evidence for the age of its controls, and mixed-vintage hardware within one console is an expected rather than an anomalous finding. This is a limit on inference, not a dating method: dating a console’s controls requires documentary evidence such as builder records, nameplates, and service records, not appearance alone. Even the nameplate needs reading with care. Engraving services sold to the trade have covered stop labels, custom marker plates, builder’s plates, and divisional nameplates, and because a plate can be made at any time, a nameplate establishes a claim of authorship and not, by itself, the date of the console or of the controls around it. A jamb of stopknobs in a uniform style is likewise not by itself proof of originality, because exact copies are what conservation guidance recommends when a knob has become unusable.

Whether original stop controls may be replaced is answered differently by two documented positions, each within its own scope. The American Theatre Organ Society’s restoration guidelines, adopted in 1992 for theater organs, state that keyboards, stop controls, and other console components should be kept in, or restored to, their original condition, and that careful thought should be given to retaining the original stopkey actuation system. The same guidelines permit a solid-state combination action or relay system where major alterations are necessary to meet contemporary musical needs, provided it equals the aesthetic appearance, feel, and functionality of the original console controls, and they note that an original setter board may remain installed for historical purposes but disconnected for practicality. A disconnected setterboard left in place is physical evidence of an earlier system, not evidence that the earlier system is still in use. This is guidance for restoration projects, not a rule applying to every instrument or every owner.

The New South Wales heritage conservation guide for pipe organs, published in 1998 for instruments of historic value, discourages replacing original stop action at all. It states that old stop labels which have become illegible should be restored to their original appearance or replaced by new ones in the same style as the originals, and that exact copies should be made of old stopknobs which have become unusable rather than fitting knobs of a different style. The two positions differ in what they permit, and they are stated here for their own scopes, a theater-organ restoration on one hand and an instrument of historic value under a heritage framework on the other, without treating either as the general rule. For an owner weighing a console rebuild, the consequence is that the conservation position for the instrument has to be settled before the stop controls are specified, and that whatever is retained or replaced should be recorded, because the console’s appearance will not record it afterward.