KMI's K‑Board Pro 4 offers one of the most cost-effective ways into the enticing world of MIDI Polyphonic Expression.
MPE (MIDI Polyphonic Expression) has been rearing its head as a concept ever more frequently in recent years, driven largely by innovative MIDI controllers like ROLI's Seaboards, the Linnstrument, and the Haken Audio Continuum. MPE is an extension, now officially adopted, to the standard MIDI specification that dates all the way back to the early 1980s. In essence it's a scheme that assigns each played note its own MIDI channel, to allow independent finger-driven vibrato and bends, polyphonic pressure/aftertouch, and generation of CC messages from front-to–back finger-slides, using a suitable 'expressive' control surface. For many styles, an MPE controller can be responsive and musically intuitive in a way that a conventional piano-style controller can't match.
The Keith McMillen K‑Board Pro 4 is, at the time of writing, the most recent MPE controller to come to market, but it's not the California-based company's first. The tiny, low-priced QuNexus has been available for some years, but its two octaves of pad-like keys don't necessarily appeal to serious keyboard players. Interestingly, the K‑Board Pro 4 (which I'll refer to as the KBP4 from now on) first came to light as a Kickstarter project back in 2016. Whilst it took a longer time to become a reality than was originally envisaged, it's very much here with us now, and shipping in good numbers.
Compared to the QuNexus, the new controller is a different kettle of fish. First off, it's physically much heftier, at 66 x 21.5 cm, with a four–octave keyboard (though one that unusually spans C to B, rather than C to C). The keys aren't pads any more but more or less full piano–key-size silicone strips, which, despite standing proud of a smart metal casework by a few millimetres, don't actually move. They're supplemented with four backlit 'slider' strips running horizontally above the keys, which let users tweak settings in real time. For many users, the KBP4 will find a natural role tethered to a computer DAW setup, but it also has the potential to flourish in hardware-based rigs as well, in conjunction with a dedicated MIDI Expander (see the 'Hardware Store' box). Either way, it's USB-powered, can store four presets in hardware that recall different modes of operation and controller mappings, and has dedicated sockets for one switch-type pedal (of either polarity) and one expression pedal. The 'cyberman ears' design you may have seen in some prototypes, incidentally, did not make it through to production: something I feel relieved and sorry about in equal measure. A dedicated hard case is available for around £150$149.
Examining the 'keys' in a bit more detail, they both look and feel slender, and are measurably so as well. Where a standard synth's octave spacing (measured from the middle of two adjacent Cs, for example) is 165mm, the KBP4's is a svelte 154mm, and front to rear the naturals measure 128mm. The blue-topped sharps are particularly narrow and sit proud of the naturals by a couple of millimetres. Key surfaces are lightly textured, but allow the fingertips to easily slide back and forth. As I mentioned, the keys don't move in the traditional sense, and there's no 'mechanism' as such. Striking a note or chord feels like tapping or touching an inert surface like a tabletop, but applying pressure reveals a slight give, up to about a millimetre perhaps. Nothing like as much as a ROLI Seaboard's malt–loaf sponginess, but noticeable none the less. As for the horizontal control strips, they're shallower, have even less give, and clearly aren't designed for the same kind of expressive physical interaction.
It's interesting to note, by the way, that the KBP4's keys really are...