The U-648 is big and beautiful, with a handsome hardwood frame and a generous 288 hexagonal keys. Four knobs and a joystick are provided, along with basic pedal inputs. The operating system is not fancy, but it’s packed with features.
You can split the keyboard into numerous zones (which can overlap) and create separate keymaps for various zones, so the actual layout of MIDI notes can be complex. The layout of black and white key tops makes it easy to visualize standard 12-note-per-octave scales along every two rows angling upward to the right, but the U-648 is a special-order item, so you can specify a different arrangement of black and white key tops if you want to. (I recommend against an all-white keyboard because having some visual feedback is very useful.)
The keys are velocity-sensitive, and velocity curves offer customized response. Even so, I’m not convinced that the velocity response of the U-648 is as smooth as on a good conventional keyboard, if only because there’s very little physical key travel. As a result, finger movements seem a little harder to control.
You can easily play glissandi by sliding a finger along a row or column. The keys rock back and forth a bit to accommodate this move. As a result, they feel a bit spongy. You’ll need to practice to create a smooth, musical playing style—and also to learn the shapes of the chords and scales, of course.
After creating a layout for 31-note equal temperament, I found the U-648 absolutely liberating to play. Harmonic and melodic patterns that are hard to find on a conventional keyboard were easy to find, and transposition was a no-brainer. I later tried my layout (that is, my assignment of MIDI note numbers to the U-648’s keys) with other equal-tempered tunings, including 12, and found it effective in all of them.
The challenge, I found, was learning to think in two dimensions. A conventional keyboard is left -to-right linear. The geometry of a twodimensional hex layout is more complex. In addition, the U-648’s key tops are smaller than those on a conventional keyboard, and the hand tends to cover up a bunch of keys visually. As on any alternative keyboard, practice is required for mastery.
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