Korg RK-100S keytar with built-in synth reviewed

With the keytar comeback in full swing, it was only a matter of time before companies like Korg began to delve into their own back catalogs for inspiration. The new RK-100S combines a classic look and Korg’s current analog-modeling synth technology in a compact, wearable unit. We grab the included strap and take it for a spin.
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With the keytar comeback in full swing, it was only a matter of time before companies like Korg began to delve into their own back catalogs for inspiration. The new RK-100S combines a classic look and Korg’s current analog-modeling synth technology in a compact, wearable unit. We grab the included strap and take it for a spin.


The RK-100S has a striking design reminiscent of its namesake, the RK-100 (first released in 1984), and comes in a red, black, or white finish. The new model is more compact than the original, thanks in part to its 37-note “slim-key” keyboard (the same as the MS-20 Mini). The keys are velocity-sensitive, but there’s no aftertouch. There are two ribbon controllers: a short one on the neck, and a long one that runs below the keyboard. A three-digit LED display and an up-down lever facilitate changing programs. You can also access banks of favorite patches by selecting one of the eight buttons above the right side of the keyboard. These buttons also light up when you play the keyboard (just for eye candy) and act as indicators/switches for arpeggiator steps.

Above the left side of the keyboard are four more backlit buttons: Tap (tap tempo for arpeggiator, LFO, or delay effects), Arp (arpeggiator on/off), Short Ribbon (changes neck ribbon function between pitch-bend and modulation), and a Shift button to yield a few more functions when used in conjunction with other buttons. The neck has octave-shift buttons, plus two buttons for assigning the function of the long ribbon (either pitch or filter control). Connections are found on the right side of the instrument, except for volume dial and audio output, which are on the front panel. The 1/4" audio jack carries a stereo signal suitable for headphones. It will also accept a monaural 1/4" cable (outputting the left channel only) or stereo Y-cable. The RK-100S is powered by six AA batteries (included), or by an optional AC adapter.

Built-In Synth

The field of keytars that generate their own sound (as opposed to being strictly MIDI controllers) is a small one. Among these, the RK-100S is the only one we know of that employs analog modeling synthesis. Under the hood is a full-featured synth engine derived from the MicroKorg XL+. Referred to as MMT (Multi-Modeling Technology), the engine models classic analog and digital waveforms, and includes a vocoder.

Each program contains up to two “timbres,” which can be layered or split into different key zones (or different MIDI channels in Multi mode). A program with a single timbre has eight-voice polyphony, which is halved when the vocoder or a second timbre is employed. Each timbre has two oscillators plus a sub-oscillator. The available waveforms include saw, pulse, triangle, and sine waves; oscillator 1 can also generate formant, noise, and a selection of sampled instruments and single-cycle waveforms reminiscent of Korg’s DW-6000 and DW-8000 synths. There are multiple modulation routings, and a “virtual patch” matrix of five different modulation source/destination pairs. Each timbre also features a two-band EQ. Each program has two master effects, with 14 choices including reverb, delay, compressor, tape echo, ring modulator, and more.

RK-100S Editor

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You don’t edit sounds from the RK-100S front panel, but from the RK-100S Sound Editor Software, which is a free download (shown at left - click image to enlarge). The main screen features a library of the 200 presets, plus a list of presets assigned to the eight Favorites buttons on the RK-100S. The preset list reads like a spreadsheet, the columns of which aren’t labeled; click on the Column button to see what the columns are really telling you. Click the Edit button to display the program’s overall parameters, including an Edit Synth button to reveal further parameters for each timbre, with a soft-synth type of graphical layout. This window reveals what a capable and versatile synth the RK-100S is.

In Performance

When I first donned the RK-100S, it was noticeably heavier than expected. Despite its compact form, it’s fairly dense at seven and a half pounds. One might not notice the wooden construction, because all colors of the RK-100S have glossy painted finishes. The slim-key action feels easy, as you’d expect, though players used to full-size keys may have to get accustomed to the approximate 75 percent scale. The ribbon controllers are responsive and fun, and each can serve multiple functions. The short ribbon on the neck can be assigned to either pitch-bend or modulation. When the ribbon is assigned to pitch-bend, you slide up (right) or down (left) to bend pitch accordingly; releasing the ribbon snaps the sound back to its original pitch. When used as a modulation controller, you slide up from the leftmost side of the ribbon to increase modulation. Curiously, the short ribbon function switch is found on the keyboard panel, making it inconvenient to change rapidly between pitch bend and modulation control. (You must either remove your left hand from the neck, or take your right hand off the keys and press the button.) There are, however, neck controls for the long ribbon functions. It would have been great to have the short ribbon control button on the neck with them.

The long ribbon has a couple of useful implementations. In one, it’s a playing surface—just slide your finger across the long ribbon to play a scale with programmable note and range values for each preset. In another, it offers a unique take on pitch-bend. While playing a key with the right hand, you can press one of the two Long Ribbon buttons on the neck (pitch or filter). This will sustain the note you played, freeing the right hand to use the long ribbon for an upward wide-range pitch bend or filter modulation.


The RK-100S is a serious looker, and a match made in heaven with its retro-friendly synth engine. It’s hard to put this instrument down, or, rather, take it off. It’s a fitting tribute to the original RK-100 while packing enough forward-looking inspiration, expressive possibilities, and cool factor to spare.


Sleek, elegant, classic design. Solidly built. Powerful synthesizer with effects and arpeggiator onboard. Second ribbon controller runs the length of the keyboard for alternate control possibilities.


Keys aren’t full-size. No aftertouch. Wood body looks great but adds unnecessary weight.

Bottom Line

Korg’s new keytar has real stage presence, with a sexy retro look and real sonic muscle.

$899 list | $700 street | korg.com