WX7 Keyworks Modifications for 4-Valve Playing
For brass players interested in a "valve type" keyworks on a wind synthesizer, there has typically only been wind controllers built around the Akai EWI electronics platform. Specifically, the Akai EVI1000, and the Steinerphone, both which were designed by Nyle Steiner. There was the Crumar wind synthesizer from the pre-midi days too.
But, for the person who likes the Yamaha WX7/WX11/WX5 type platform with it's pitchbend reed controller, there has been nothing to allow the brass player to use a 4-valve fingering system.
This article describes a "first effort" at a custom modification that I did to retro-fit a WX7 for 4-valve fingerings. This is only an experimental design, and not meant to be anything more than an exploration between Steve and me to see if continued development work is warranted. It is based on the use of non-invasive wiring changes inside the WX7, as well as external switches. Being experimental, this was acceptable. Should the implementation of a 4-valve fingering method prove beneficial, then a future goal would be to design a replacement keyworks PCB that would 100% internalize the electronics and switches.
This was the 'quick and dirty' method, and I still plan on completing my design that is fully programmable. Upon inspection with my oscilloscope, the computer scanning of the WX switches was more complicated than I anticipated, so a programmable PAL approach was going to take real thought. That was aggravated by the fact that my good oscilloscope (scope) died a few years ago, so I've been using a less useful scope, and that was making the key scanning stuff that much more difficult to reverse engineer.
I always suspected that 'rewiring the switches' would work, but dismissed that as not as flexible as my PAL approach. So, one nite I worked with my WX7 and looked for logical key combinations that act like EVI .5 step valves. This really distills down to Boehm vs. Valves.
Now, to digress a moment, let's think about woodwinds and Boehm. Woodwinds are not characterized by the note played when all key are 'open', but instead when all are down. That's the max. tube length. This tube length then is shortened as you progressively open holes. Each hole is positioned for either 0.5 step or 1 step, per the given scale to which the instrument is to be pitched. You know, major scales are HHhHHHh (where H=whole step, h=half step) for C-Maj. So, but adjusting tube length and hole positions (ie. where are the half steps), any key can be accommodated, but the horn is specific to it's manufactured key. Then, along comes a progression of technical advances, culminating in Boehm's work which yielded a fully chromatic keyworks. Flute and sax are almost the same. Oboe and clarinet are really similar (though clarinet overblows 12ths instead of octaves).
The Boehm system handles half steps through fingerings which are really similar to a trumpet. The Boehm keyboard is essentially 6 keys (3 for left hand on the top half of the tube, 3 for right hand on the bottom half of the tube). A C instrument actually produces a C# when no keys are closed, and a D when all keys are closed. Max tube length to get to the low C is via an added 7th key on a lever for the right pinkie. Anyway, this is digressing too far. Suffice it to say that on Boehm, all keys open yields C#. Center hole closed on left hand drops the pitch by a half step (like trumpet) to a C. Open that center key and instead close the top key and a B sounds (hole step). Close the top 2 keys and you get an A. Here's where the Boehm deviates from trumpet. Looking at this diagramatically:
trumpet boehm boehm note 1 2 3 1 2 3 highest note 0 0 0 0 0 0 C# -1 half step 0 * 0 0 * 0 C -2 half step * 0 0 * 0 0 B -3 half step * * 0 * 0 0 + extra key Bb -4 half step 0 0 * * * 0 A
On the WX, there are several of the noted "extra keys" like I show above to flat the B. Some move the tone up a half or whole step, and others lower a half or whole step. Sounds like it's easy. The problem is that the logic on the WX makes it so sometimes these keys are not activated, to keep to the true Bohem standard. That's why flute players or recorder players sometimes grouse about the keying. The small differences between flute and sax show in the WX implementation of Boehm, which is closer to a sax than a flute. Also, the WX has additional alternate fingerings that exist only in the WX for help in octave switches without glitching, etc.
Anyway, puttering with my WX, I could get several key combinations to mimic the first two trumpet valves, but not the third or not the fourth. Or, if I found the third, then the second would not work. Not finding a successful combination externally to the WX, I removed the key PCB from the body, hooked it up to my FM synth and my tuner, and started puttering with non-logical key presses, trying to exploit the WX alternate fingerings in offbeat ways. This worked. I found a combination where if I used reverse logic - key depressed = valve *not* activated - I could get the proper combination for the first 2 keys. This reverse key logic would be akin to keeping 3 of your WX keys sprung in the down position, and lifting 2 of them to actuate the key (the third is always pressed and doesn't ever get actuated - it just puts the other switches into range).
So where does the G# of "all open" come from? Well, it just so happens that when you spring these 3 keys down, the built in WX alternate keying yields a G#. Again, I don't care, because that's an easy fix with an Anatek Pocket Transpose or similar. I just want a combination that works like trumpet valves.
Once the keys were identified, I soldered and clipped in external switches which worked the opposite of the WX keys. They *closed* the circuit when not depressed, and opened the circuit when depressed. Many button switches have extra terminals so they can be wired either this way, or the typical press=closed way. Actually, only keys 1 and 2 are 'normally closed', and key 3 is 'normally open'.
That was the first wiring configuration. After your discovery of a 4th key error, I again puttered with odd key configurations, and found another that functioned properly, including the 4th key. This odd combination yields a C# when blown with no keys depress, and again will need to be transposed via synth or Anatek Pocket Transpose to match a trumpet's open blow of Bb.