| 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?
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