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The 'halfmoon' switch has been around for more than 60 years.  In fact, it wasn't even invented by the Hammond Organ Company -- it's from the early days of Leslie Speakers.  Most organists who kick pedals, or stand while playing, find controlling the Leslie speed with a footswitch less than optimum, and the halfmoon switch provides an attractive alternative.  So why isn't there a standard for the wiring of these switches?  Well, there is:  in fact, there are almost a dozen of them!

 
Choose Your Weapon

Every halfmoon switch I've ever seen uses two or three wires, often attached to a 1/4" phone plug.  It would seem that this would lead to a very few options, but different companies have chosen their own ways to interpret the wiring.  If we look at a 'stereo' (TRS) phone plug, there are three connections:  the 'Tip,' the 'Ring' and the 'Sleeve.'

Usually, the Sleeve is used as a common (or 'ground') point, but this doesn't have to be the case; Ring- or Tip-common wirings also work.  This leads to 12 possible connection schemes -- except that it's really twice that many, because tying a signal to common can mean something happens, or that same something stops happening.

 
The Original Standard(s)

Don Leslie's early speakers had one speed, Tremolo; otherwise, the speaker stopped (Off).  Later models added Chorale in place of Off to provide the kind of movement that a rank of organ pipes provides.  A second motor was added to each rotor to provide the other speed.  Either way, Leslie halfmoons used 2-wire cables; and for reasons that I won't get into here, connecting the two wires together created Chorale/Off speed.

By the time the '70s rolled around, players wanted both Chorale and Off, and Leslie provided this by 9-pin, and later, 11-pin interfaces.  In both cases, a low-woltage signal was grounded to run the Tremolo motor; and a different one grounded for the Chorale motor.  Grounding neither one meant that the Leslie stopped.  This method allowed connecting directly -- and safely -- to a halfmoon switch, and the scheme was kept by Hammond when they bought Leslie Speakers, and later by Suzuki.   This is the most common wiring standard for 3-way halfmoon switches.

 
The Plot Thickens

As other manufacturers entered the picture, things quickly got complicated.  The Leslie/Hammond standard makes sense in vintage Leslies with two-stage motors, but maybe not with a single motor that creates both speeds, or with rotary simulators.  Modern customers want to connect a variety of pedals to their Leslie or sim:  'gas' pedals, sustain pedals, etc.  Certain wiring schemes make it easier/harder to detect and support these alternate devices.  So, designers chose their own paths.  Some of the methods partly overlap with others, but aren't fully interchangeable.

In a perfect world, the teams would have met and standardized on one halfmoon wiring scheme, weighing the pros and cons of different approaches, but halfmoon switches have always been a niche market, and it never happened.  So, how does it all shake out in today's world?

Halfmoon Wiring Standards
Standard Speeds Vintage Ham-Suz Leslie Korg Roland Motion
Sound
Clavia (Nord) Neo
Vent
GSi
Burn
DMC-122 Mojo Mojo
61
Numa
Organ
HX3 Dr. Fish
Leslie 122/147
(TS plug added)
S/F X     Some Some 2-spd NE3/NE4,
Stage 2/EX,
Stage 3
              2-spd
Inverse 122
(Shorted = Fast)
S/F   XB3, XK2   Some Some   NE3/NE4,
Stage 2/EX,
Stage 3
            2-spd 'S' -> F
'F' -> S
Hammond CU-1 S/O/F 2-spd XK1c, XK3/XK3c,
SK1/SK2, XK5
Cream
Pedal
      C1, C2/C2D,
NE5/NE6,
Stage3, Stage4
(Compact)
Vent 1/2              
Motion Sound S/O/F       Some   X                 'S' -> F
'F' -> S
GSi Burn S/O/F                 X X   X      
Crumar Mojo S/O/F                     X        
Kbd Part HX3 S/O/F       Some                   X Inverse
Dr. Fishsticks S/O/F       Some                   Inverse X

Copyright © 2019-2023 by Bruce Wahler.  If you have suggestions, please send them to bw@wahler.us.