This is a stop junction in the right blower room.  All wires from both consoles junctioned here and were distributed to chambers.  We “tap into” the original stop sense signals here to avoid disturbing the wiring harnesses in the console itself.

This is a stop junction in the right blower room. All wires from both consoles junctioned here and were distributed to chambers. We “tap into” the original stop sense signals here to avoid disturbing the wiring harnesses in the console itself.

The Atlantic City Midmer Losh organs is one of the most incredible musical instruments ever created by man. Because it is being rebuilt in phases over time, the phases aren’t necessarily aligned with what would be ideal from a control system perspective. Most control systems require console information to be relatively close together, but until the 7 manual console is rebuilt, it is spread around the building. Hall effect keystrips were retrofitted into the keyboards, providing a source of keying in the console. Linear transducers are also retrofitted to the original swell shoes in the console. Coupling originally occurred in Reisner-Style keying trays in the console, so coupler signals are available in console junctions. Stop signals do not junction in the console at all, and are wired to junctions in the basement (pictured below). A small card panel in the right side blower room collects the stop statuses and forwards them back to the console.

There are currently 7 chamber relay panels with a total of nearly 100 I/O cards just driving pipes. Another dozen cards is used in the collection of stop source data from various locations around the hall.

There are a number of features that were original to the instrument, including melody couplers, pizzicato couplers, and floating divisions. These are all recreated in software to work exactly like the original pneumatic units.


Some fun facts:

  • There are 87 “global” couplers in the organ. Global couplers affect all controllers. In addition, some controllers have as many as 20 “local” couplers - these are couplers that only affect a particular chamber controller card.

  • One of the largest causes of dead notes we found during an early survey of the organ was key contacts. Because one key contact can take out many pipes, these become very important to eliminate as a source of trouble. The hall effect key strips on the manuals are impervious to humidity and automatically adjust for changes in physical key caused by seasonal climate changes.

 When panels are wired, each cable is labeled with stop number and note numbers to aid future troubleshooting.

When panels are wired, each cable is labeled with stop number and note numbers to aid future troubleshooting.


Each :

  • Each chamber stop control is routed through that particular chamber’s Controller Card

  • The console scanning matrix keep track of whether the console is actively being played or not and includes that information in the frames sent to the chambers.

  • If the console is not being used (and hasn’t been for a few minutes), the chamber tuning controls are allowed to turn stops on and off. This prevents stops from being “left on,” which was a periodic problem in the past.

  • Opus-Two Wireless Tuning Keyboards are also enabled or disabled based on the console activity status.

The Pedal Divide System

  • One of the many features requested by the curator staff was an adjustable pedal divide with multiple operating modes.

  • The Pedal Divide split point should be settable on any piston and should default to note 12 (low B).

  • A button was located to be used as a “set button” for the pedal divide – simply hold down the pedal and press the button and a new split point has been set.

  • In order to store that split point on the pistons, a clever technique was devised to allow the Opus-Two relay and the Peterson Combination Action to communicate.

  • There are three Pedal Divide Controls: Pedal Divide, Pedal Divide Right, and Tuba Magna on Pedal Divide. Pedal Divide (normal) takes the native pedal stops and plays them up to the divide point, (only) above the divide points, any couplers that couple “to Pedal” play. Pedal Divide Right allows the “to Pedal” couplers on the left hand side of the console to couple with the native pedal stops on the “lower half” of the divide, but the “to Pedal” couplers on the right hand side of the console get restricted to the “top half.” Tuba Magna on Pedal Divide does just what it says – Pedal Divide on the upper half.

The Expression Coupling System

  • The original expression coupling system was originally a series of pneumatic coupler switches, similar to the divisional key coupler switches in use until the 2013 changeover. A Peterson Diode-Matrix was the first electronic replacement for the key coupler switches.

  • Several of the organists desired features for expression coupling would have been very difficult to accomplish with Diode-Matrix technology, making the expression coupler system a natural inclusion with relay replacement.

  • These “exotic” features include making some expression shades follow the keying couplers (for example, if “Celli on Choir” is pressed, the string shades in front of the Celli stop tracking with the rest of the string and start tracking with the choir shoe). Another feature is the reversing swell shoe – it forces a second shoe to be “opposite” the first – as one shoe is opened, the second closes. As the first closes, the second opens.

  • Some features that were intended but (for whatever reason) were never implemented were able to be implemented. These include things like the Choir Expression Master.

  • Previously, the expression sliders under each keyboard were physically wired with the expression shoes. They are currently read separately and merged in software. On command, either the shoes or the sliders can be “separated” from the other. These separated sliders can be coupled to, and used to control tremolos, for example.

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