Jim Aikin's Oblong Blob

Random Rambling & Questionable Commentary

Fun with Isomorphism

Posted by midiguru on November 27, 2012

Every musical instrument has limitations, not only in terms of its range and timbre but in terms of the mechanical possibilities it provides. If you want to be able to play chords, a clarinet would be a poor choice — as would any wind instrument with the possible exception of the bagpipes or the harmonica. Conversely, if you want to hear tones that will sustain indefinitely, don’t write for piano.

If you want to be able to play more than 12 notes per octave, your options will be even more limited. A number of software-based synthesizers will make wonderful sounds while producing whatever tuning you can devise, but playing any of them from a MIDI keyboard will present some unusual challenges. Figuring out how to finger scales and chord voicings for a tuning with 31 notes per octave while playing a standard 12-note-per-octave black-and-white keyboard … well, it’s possible. I’ve done it a lot. But it’s a brain-twister.

Having done a bit of research over the years on alternative MIDI controllers, this fall I ordered a Z-Board from Starr Labs. I was aware that it wouldn’t have or be absolutely everything I could ever desire, but I was also pretty sure it was the best instrument I was going to find. It arrived yesterday.

The Z-Board has quite a lot of software smarts packed inside, but that’s not why I wanted it. The keyboard is a 12-by-24 array of velocity-sensitive buttons, and this array has the enormous advantage that it’s isomorphic. That is, a given chord or scale has exactly the same shape, no matter what key you start on. (The array of black and white key tops is arbitrary, and in fact the pattern shown in the photo is not the final arrangement that I settled on — it’s based on an earlier diagram I had sent them. Oops. We’ll get that sorted out in a couple of months. No hurry.)

Any key on the Z-Board can be programmed to send any MIDI note number you want. In fact, the features are more comprehensive than that: You can program various maps of keys to MIDI notes, assign the maps to various zones on the keyboard, and so on. It also has a joystick, four knobs, and a ribbon controller, all highly programmable, plus the usual rear panel inputs for sustain and volume pedals. The USB output is class-compliant, and the unit can be USB-powered, so it’s totally plug-and-play. I connected the cord to the computer, launched Cubase, loaded Zebra 2, and started playing.

The first thing I noticed was that I was getting an awful lot of double-strikes. I would tap a key and hear a little stutter at the beginning or end of the note. After panicking briefly, I paused and read the manual. By setting the sensing threshold somewhat higher (see, I told you there were a lot of features in the OS), I was able to lower the incidence of double-strikes.

But they weren’t eliminated by any means. And thereby hangs a tale.

One of the limitations of the Z-Board is that there is almost no key dip. The amount by which a key travels downward when you strike it is no more than a millimeter. As a pianist, I’m used to keys that travel downward very significantly at the beginning of each note. Thereafter, the way to keep the key pressed down is to relax. The relaxed weight of the finger is all that’s needed. Continuing to exert pressure after the key has reached the keybed is very poor piano technique. It doesn’t accomplish anything, and it leads to tendon stress.

Stringed instruments behave differently. When I play cello, of course I have to continue to press the string against the fingerboard all the way through the note. A guitar works the same way: You can’t let your finger relax too much while the note is sounding; if you do, you’ll hear fret buzz.

The ancestry of the Z-Board is Starr Labs’ Z-tar. I was trying to play it like a piano, when it was built, in the first instance, for guitarists. Once I started playing the keys with very definite keystrokes and holding the key more firmly rather than relaxing, the stuttering artifacts became much less frequent. And that’s with one day of practice.

When I acquired a five-string electric cello a few years ago, it took me a couple of months to master the technique. It’s a cello — and yet it’s not. There are five or six subtle but definite differences that I had to learn. I expect my experience with the Z-Board will proceed much the same way.

I’m also remembering something Jack Hotop said when the Korg Wavestation came out. Jack was a Korg guy, and called upon to play the Wavestation at high-profile trade shows and such occasions. The Wavestation could play a whole rhythm sequence from one key. If you struck and held one key and then struck another a quarter-note (or three eighth-notes) later, you’d get a more complex and interesting rhythm. But you had to strike that second key at exactly the right moment, or the two rhythms would be a train wreck.

I vaguely remembering Jack saying, “I decided I was going to learn to do that.” And he did. It really is possible to play two or more keys at different times with precise rhythmic coordination, but it takes practice. Playing the Z-Board so it doesn’t produce stuttering double-strikes — same deal.

I’m already discovering that the isomorphic layout is exactly what I was hoping for. It’s a brain-twister in its own way: Keyboard players are used to thinking of the notes in a scale as being laid out in linear fashion from left to right, but scales and chord voicings on the Z-Board are two-dimensional patterns.

The patterns depend both on the MIDI note layout and on the chosen tuning. This is a complex subject, and I don’t propose to try to explain it tonight. Maybe later. At a basic level, using the default factory note layout, the Z-Board is laid out like a guitar with 12 strings tuned in 4ths. The “strings” are the rows running from left to right, and as you move up in a column, the pitch ascends in 4ths. With 19 notes per octave, the 4ths turn into minor 3rds — still the same number of scale steps (5), but the musical interval is smaller because the scale has more steps. With 31 notes per octave, when you play up a column the pitch ascends by a major 2nd (still 5 scale steps, which are now quite close together).

The point of this process is that it becomes much, much easier to find harmonic patterns that you would never think of if you were playing the same tuning on a standard keyboard, because your hands wouldn’t go there. Here’s a quick example:

That’s 19 notes per octave, a sequence of major 6ths. The chord would sound unbearably thick if the notes didn’t die away, harpsichord-fashion, but with the right sound, you get a harmonic spiral that ascends into outer space.

As a side benefit, one hand can reach larger intervals than on a standard keyboard. Even with 19 notes per octave, I can easily span three octaves with one hand.

Learning to play two-handed … well, that’s going to take a little more practice.

4 Responses to “Fun with Isomorphism”

  1. georgek said

    Wow, that’s awesome. How long is it relative to a piano keyboard?

    • midiguru said

      The key area is 21-1/2 inches long by 6-1/2 inches deep. A standard 5-octave MIDI keyboard is about 33-1/2 inches long, so the Z-Board is rather compact. I wouldn’t actually mind if it were a bit bigger, but the keys are comfortably sized for my fingertips.

  2. C.L. said

    Have you seen or tried the Tonal Plexus keyboard yet?

    • midiguru said

      I’ve looked at pictures and read descriptions on the Web. The buttons are not velocity-sensitive, which I find a bit discouraging, and the way they’re laid out seems to bias the music in the direction of a conventional diatonic tonality (with added pitches that are slightly flat or slightly sharp). I’m not sure how well it would work as a general-purpose keyboard for playing VSTs. In sum — I’m glad it exists, and I think it’s terrific that people are using it to make music, but it isn’t quite right for me.

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