Decades ago, capacitance-based controllers were popular among synth users because of the pressure sensitivity they provided. Typically, this was created by measuring the amount of skin that came into contact with the touchplates: The harder you pressed down, the more your finger spread across the surface and the greater the change of voltage at the pressure output—perfect for adding subtlety to a patch.
The Holy Grail of capacitance controllers were built by Buchla & Associates for its ’60s- and ’70s-era systems and were available in several configurations. However, the Model 218 and Model 221, as rare as hen’s teeth these days, simulated a 12-note per octave keyboard, dispelling the myth that the company’s founder didn’t like the standard layout.
Verbos Electronics (verboselectronics.com) has granted the wishes of many modular users by introducing a standalone capacitance-based controller, the Touchplate Keyboard ($799). Though it is designed to fit into a Eurorack case, it can be used with any synth that supports 1V/octave control voltages. Touchplate Keyboard can be powered either by a standard Eurorack ±12V system or an external, positive-tip DC power supply that provides 9-15V.
Portability is a big plus: Together, the controller surface and circuit board are 0.75" thick. Consequently, the controller can be housed in a shallow skiff or other table-top case independent of your modular system. That’s handy, because at 84HP (16.75"), the Touchplate Keyboard is fairly wide; it’ll fill an entire row of a Doepfer A-100P case.
The control surface has four distinct areas with gold-plated contacts: a 32-note 2.5-octave keyboard with individual outputs for CV, pressure (+9V), gate (+5V), and trigger (+5V, 10 ms); three octave-select pads for the main keyboard; an independent pair of pressure-sensitive bender pads (±3V); and eight individually tunable pads that share a separate set of CV, pressure (+9V), and gate outputs.
A traditional approach to using the Touchplate Keyboard would be to treat it as a piano-style controller that triggers single notes, perhaps using the Bender to alter pitch and the tunable pads to incrementally open and close a filter. However, this surprisingly simple interface can be configured in more complex ways. For example, the upper row of pads could be used to control a monophonic bass instrument or select the transposition pitches for a sequencer (with the pressure output adding modulation), while the main keyboard controls another voice and its pressure output controlling a different type of modulation. Meanwhile, the CV output of the bender pads can be routed to additional parameters connected to either voice or both. As with the keyboard, only one of the tunable touch-pads can be active at a time.
Keyboardists who have never played a capacitance-based controller will have to adjust their technique, because the control surface is flat, with the accidentals raised just enough that you can feel where they are without looking. The upper row of contacts (where the Bender, Octave, and tunable pads sit) is also minutely elevated.
Overall, the controller responds quickly, but a light touch provides the most subtlety. And that is what the Touchplate Keyboard is all about: It’s an easy-to-use interface that puts a wealth of control options under your fingertips.