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I teach in Oregon City and online videochat. I work with all ages and levels and a variety of styles. I specialize in creative exploration, the psychology of music, and conscious music practices. Visit the lessons page to learn more.

Saturday, March 19, 2011

Tonal Plexus microtonal keyboard: 3 videos

In 2008, I became one of the first owners of a Tonal Plexus keyboard from H-Pi Instruments (a mostly one-man production of owner Aaron Hunt, who hand-builds the keyboards and creates the supporting software).

I had already deeply studied pitch in music through barbershop harmony, alternatively tuning my guitars, listening to software tone generators, listening to a wide variety of music from around the world and from composers who explored pitch (such as Lou Harrison, Harry Partch, Toby Twining, Jon Catler, and many others), and through extensive reading (including Hermann Helmholtz, Easley Blackwood, Bill Sethares, and many more).

At one time, I had hoped to find some simple scale or guitar tuning or guitar fretting system that would achieve the sounds I was seeking; but no optimal system seemed possible. If I wanted one chord tuning, it interfered with tuning another chord. Frets would have to be so close together, that I might as well have no frets. No frets allows any pitch, but then it is much harder to avoid errors in tuning. Violinists and barbershop singers work hard enough to get one pitch tuned just so. Achieving consistent accuracy (to the degree that I want) with multiple notes and complex chords all on a single stringed instrument is unrealistic.

With the Tonal Plexus (TPX) keyboard, a whole new flexibility is possible without sacrificing accuracy. The sheer number of pitches approximates a complete pitch continuum. In other words, the very low-bit digital system of the traditional keyboard or fretted instruments is rough and blocky, like an old eight or sixteen color computer screen, whereas the Tonal Plexus is still digital but is more like 8-bit or 16-bit color (meaning hundreds to thousands of colors) on a computer monitor which can much better approximate the full color spectrum. Full analog devices are completely continuous, but being digital offers more accessible accuracy. I can press a specific button and get a specific predetermined pitch.

On the downside, the TPX cannot achieve the natural fluidity of analog instruments like fretless strings or the human voice. Also, the lack of touch sensitivity further limits the keyboard's expressive potential. Of course, adding touch sensitivity for so many buttons would make the instrument prohibitively expensive, if it were even possible. At least there is a randomization option for velocity as well as a whole-keyboard option for volume and velocity control via footpedals. It is worth noting that harpsichords and organs have still been used to make effective music despite their lack of touch sensitivity.

While I learned much upon initially playing with the keyboard, I found it frustrating that it still could not achieve quite what I wanted. The stretches seemed awkward. I wondered about all sorts of other alternatives. I decided to finally get a fretless guitar (see my 2009 video). The guitar's nuances and fluidity were thrilling, but it wasn't the full answer either. I've come to accept that my imagined complete instrument may simply be practically impossible (even though simultaneous fluid melodic motion, precise harmony, harmonic deviance, and control of touch sensitive nuance is — in principle — possible). Maybe touch-sensitive multi-touch computer screens along with some complex algorithmic tuning will get closer, but we're not there yet.

In the end, I have realized that what matters more is the human context: the cultural and psychological experience of music over the details of the objective form. And yet, I am convinced that much of the pitch subtlety available on the TPX is psychologically relevant. I have much more to study and hope to get more involved in that sort of research, but that's a subject for another time.

In an effort to be less idealistic and perfectionist, I have gone back to the TPX to show off its unique capabilities. It certainly can do particular expressive things that no other musical instrument has ever achieved. It is worth appreciating that without worrying about the compromises. All instruments bring different insights and potential, and exploring the Tonal Plexus for what it offers has been very enriching.

With help from my friend Doug Jones doing the camera-work and providing some direction and feedback, I have made an initial set of videos on my TPX. The first is an introductory explanation:

Next, a melodic improvisation over a drone:

Finally, a barbershop tag in just intonation:

[note: click the links to YouTube to read the specific descriptions I wrote of each video]

More videos will come soon. I hope these first ones highlight just a little of the enormous potential here. My future with this could include more careful practice, maybe detailed compositions, additional controllers for more timbrel and dynamic (and even additional pitch) nuance, and coordination with other instruments and musicians.

I welcome any comments or questions, though I suggest that anyone interested in the theory explore the H-Pi website first. There, Mr. Hunt has included everything from history to theory about much of the ideas behind this keyboard. He also offers software including a FREE virtual version of the keyboard (which is also used by owners to create alternate tunings or other adjustments). H-Pi also offers software for ear-training, an alternate-tuning device for standard keyboards, and much more.


  1. That is truly remarkable work, Aaron. I hope it launches your Ph.D. work.

    Derek Hatley

  2. Great stuff. To build it into an acoustic instrument would truly be a pain, unless you allocate a whole range to a single oscillator rather than individual oscillators, I guess we should stay electronic until someone develops *ahem markets* a widely accepted system.

  3. What does that tag sound like in equal tuning?

  4. @Anonymous:
    I don't have time right now to make an alternate version of the tag, but you can see the music (in Eb though) here:

    And you can easily play it using whatever synth and a normal keyboard, or program it in a MIDI sequencer to hear equal temperament.

    For detailed comparison of tuning issues, there are many sources. I actually have completed a lengthy treatise on the theory of barbershop tuning with respect to tuning theory but also to psychology and many other issues. It includes recordings demonstrating the issues and is very comprehensive yet accessible. I haven't formally published it yet, but am sharing it with interested people if they contact me to request it...

    Thanks for watching!

  5. Wow! These keypads are genius. I am amazed at how sounds came off from these lego-like pieces.