Construction of Baroque Organ Stop Controls

For many years my ‘dream’ organ had tabbed type stop controls.  Perhaps this was because most of the organs I had access to while growing up had this type of stop control. But since I had decided to build an organ case that was somewhat similar to a Baroque organ case, I also wanted stop controls that at least looked like Baroque organ stop controls.  (Sometime early on in the process I decided that I did not want to pursue touch screens for the stop controls even though they are in may ways very flexible and practical.)  The stop controls shown here were the result of several attempts at making stops that looked and functioned like those on old Baroque organs.  They are, of course, for practical reasons spaced much closer together than those in an old organ.

In our household these stop controls are somewhat jokingly referred to as the ‘BOS-5’ controls (Baroque Organ Stop – 5, where the 5 stands for the number of prototype versions that were tried before a truly satisfactory control emerged!)

The criteria for creating these stop controls were fairly simple:  They needed to look at least somewhat like older Baroque organ stop controls with square wooden shafts; they needed to have well-defined start and stop positions including some resistance when moving the control; and they needed to be reliable in both low and high humidity conditions (a notable and time-consuming failure for one early set of controls that unexpectedly became completely inoperable during times of high humidity.)

The photos and text below describe the construction process for these stop controls.  I think they are almost easier to build than to describe with diagrams and photos.

My specific stop controls were built as 10 units of 7 stops each because this was appropriate to my cabinet and the spacing and number of stops that I wanted.  They could be probably be build in larger or smaller units.  My control units are installed vertically in the case, but there is no reason they could not be installed horizontally.

First, a photo of a more or less finished unit to show the general concept.  The control shafts are approximately 3/4 inch square ash (milled to match the 3/4″ plywood thickness minus a bit for clearance). They are essentially sandwiched between a 3/4″ plywood base and a 1/4″ plywood top, and separated from each other by 3/4″ plywood spacers about 1.5″ wide (depends on the desired spacing.)  The plywood is cabinet grade plywood which has more laminations than construction grade plywood, a smooth sanded surface, and is relatively free of internal voids.  Compared to construction plywood, the cabinet grade plywood is very stable.  I doubt that these units could be built successfully with lower quality plywood.  The rear piece of wood limits travel of the stops when they are pushed in and has felt pads to minimize noise.  The small steel pieces (cut off nails) extending from the stops (to the left) about an inch from the rear serve to limit forward travel.  The total travel is about 1.5 inches. These steel pieces hit a felt pad (not visible in the photo below, but see another photo below) to minimize noise when the stop control is pulled out.  The holes at the front of the stop control shafts can be fitted with any suitable knob (of which only one is shown below.)

The sketch below shows an end view of the stop control unit to show the working components.

Each stop control shaft contains a 1/4″ cylindrical magnet (Apex Magnets) that is press fit just slightly below the surface into a 1/4″ hole.  A steel screw is located just below the magnet in the units base.  The magnet is strongly attracted to the screw and this provides a positive locking feel when the stop control is pushed in.  The degree of the attraction can be adjusted by moving the screw up or down a small amount.

When the stop control shaft is pulled out, the same magnet is attracted to the screw on the left (at about the same time the cut off nail contacts a pad.)  This second screw provides a positive locking feel when the stop control is fully pulled out.  The cut off nail (not shown on the sketch) is inserted in a slightly larger hole than the nails diameter and is held in place by its proximity to the magnet.  It can be removed easily if it becomes necessary to remove the shaft entirely at any time.

The left hand screw also serves a second purpose.  It is intentionally sized to almost reach the lower surface of the 3/4″ plywood base and transmits the magnetic field to the reed switch from Testco.com (part number CT10-1040-G1) which is held in place by the bottom piece of 1/4″ plywood.  Additional photos below show how the wires from the switch are extended through a slot in the 3/4″ plywood base to the rear of the unit.

The photo below shows the unit with one shaft removed so the screws can be seen.  The magnet is also visible in the control shaft which is turned upside down. The pads which the nails contact are also visible just to the left of the nails.

The following photo shows the bottom of the unit and the reed switches with wires extending to wiring blocks to the rear.  (The blocks for connecting the wires are a bit oversized, but I couldn’t find better ones at the time.) The switches are temporarily held in place with duct tape during construction. When completed the 1/4″ plywood base covers the switches and wires and holds them firmly in place.

The photo below shows how temporary pieces of plywood were used to locate the spacers between the control shaft locations.  The clamp holds everything in place while the top 1/4″ plywood is positioned.  The screws through the 1/4″ plywood extend through the spacers into the base and hold the entire unit together. The holes need to be pre-drilled  through the 1/4″ and 3/4″ plywood pieces to prevent them from shifting and ruining the closely controlled spacing.  Use of the temporary plywood pieces where the control shafts will be located guarantees that each shaft will fit more or less the same and minimizes the need to custom fit each shaft (although some fitting was required.)

The photo below shows the first screw used to attach the top plywood piece.

The bottom slots are cut on a table saw prior to installing the switches and wires which are eventually covered by the 1/4″ plywood bottom cover.

The holes for the screws were drilled using a drill press.

There are a lot of details involved in constructing these units, but the only real requirement is that everything be laid out, cut, and drilled with reasonable (but not high) precision.  The control shafts were treated with paste wax before their final installation. The wires from the reed switches were routed to bo10 adaptors and sm8x8 boards like those used on my pedalboard.

The stop control units were installed in a secondary plywood case with appropriate spacers and fitted with a front ‘cover’ made of red oak.  They were mounted so that they could be slid out to the rear should any servicing be required in the future.  The cases with their front covers were installed into the front of the current organ case.

Eventually I will change the ‘cover’ piece so that it will fit flush with the face of a new case.  The labels for the stop controls are currently attached to a second face piece and held in place with magnets and screws.  This arrangement, although workable, requires a lot of work for each additional organ sample set and I’m thinking about other ways to do this that might be more convenient and easier to make.  The newly available LCD stop label units look promising, but probably wouldn’t look right on my case and would definitely be outside of any current budget.

The photo below shows the units installed in the organ case as seen from the back of the case.

After using these stop controls for several weeks, I found if a stop control was pushed in or pulled out too quickly that it might bounce and not lock into position.  This problem was eventually solved by using some size 20 (0.045″ diameter) piano wire attached to the top of the rear board extending over and gently contacting the stop control shaft.  The wire was bent to provide just enough resistance so that the stops cannot travel freely enough to bounce back. (You can just see the wires and the screws and washers that hold them in place in the above photo.)  There might be other more elegant ways to accomplish this, but this solution has proved adequate and reliable.

The stop control knobs are hardly Baroque in appearance at this point.  In fact, they are actually commercially available Shaker style knobs painted to match the case.  I have a wood lathe and do wood turnings and custom turned knobs when I need them in various furniture projects, but the thought of turning 70 stop control knobs is another matter… However,  sometime before I build a final case for the organ I intend to make some custom knobs, not quite as ornate as most Baroque knobs, but more ornate than the Shaker style knobs.  They might look something like those shown below. (I no longer know the source for this photo, otherwise I would credit it.)

These stop controls have a satisfying feel, and perhaps just as importantly, they have been in use for at least 2 years with 100% reliability even on the most humid days.