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Korg SG-Rack

Stage Piano Module By Paul Ward
Published June 1998

Korg SG-Rack

A quality acoustic piano sound in a 1U rack‑mounting package? Paul Ward lifts the lid to see if there are any strings attached...

A convincing acoustic piano sound is still one of the prerequisites for most modern keyboard players and is pretty much a must for any self‑respecting commercial studio. The better piano emulations usually require a considerable amount of sample RAM to perform their tricks — sample RAM that could often be put to better use elsewhere. Several manufacturers have recognised this dilemma and packed their best sampled pianos into ROM for us to access in a more convenient form. Korg's SG‑Rack, the modular version of Korg's SG ProX Stage Piano, is the latest to take this approach, presumably to tempt those who are already happy with their keyboard, but would like to access those much‑vaunted SG piano sounds.

Raising The Standard

The build quality of Korg instruments is generally very high, and the SG‑Rack is, happily, no exception. I shudder with horror at the thought of trying to find a home in my live rack for those annoying half‑rack sound modules, with their nasty phono outputs and annoying external power supplies. No problems here; nail the SG‑Rack into your standard 19‑inch rack, plug in the Euro power cable, hoist a pair of standard quarter‑inch jack leads between module and mixer, man the MIDI sockets (In, Out and Thru) and... well, that's it really, because you've run out of holes!

The SG‑Rack's apparent simplicity extends around to the front panel, too. To the far left is the headphone socket with volume control, while to the far right is the chunky power switch. Filling the centre ground are the items of more enduring interest — 14 black buttons (set into a black background, in fine synth design tradition) and a seriously large backlit LCD. Having seen other manufacturers adopt larger instrument displays leads me to hope that the trend continues, if only for the sake of those of us having to peer nervously across a darkened stage before hitting the first key of a song.

Operation of the SG‑Rack's various parameters will be familiar to seasoned users of Korg equipment. Dedicated buttons take the instrument into Program or Performance mode. In Program mode, only one sound may be used at a time, whilst a Performance allows for the splitting or layering of two Programs. Modification of a Program or Performance is only a press of the Edit key away, with the +Page/‑Page, cursor left/right and +1/‑1 value keys being used for moving around the pages and changing settings.

Both Programs and Performances are arranged in four banks of 16, including a basic range of piano, electric piano, organ, string and synth sounds. 24Mb of sampled PCM ROM gives the module its source waveforms, with a maximum polyphony of 64 voices being delivered by the familiar AI2 synthesis engine.

Temper, Temper

Since the SG‑Rack is geared towards providing a ready‑made palette of usable sounds, the amount of editing that can be made to a Program is fairly restricted. Brightness, level, attack, decay, release (including options to simulate realistic piano damping) are all adjustable, while Key Touch allows the effect of velocity on volume and tone to be varied to suit your playing style. The tuning scale is also selectable between equal temperament, pure major, pure minor, Pythagorean, Werkmeister, Kirnberger and stretch. Each edited Program can be saved with a new name, or in the event of a sudden panic, can be restored to its factory settings — nice touch for us nervous types.

I found it difficult to stray very far from Program A01 'Concert', which is pretty much all I've ever looked for in a sampled grand.

Moving into Performance Edit allows two Programs (or 'Timbres', as they are known within a Performance) to be encouraged to co‑exist across your keyboard. Here the level, pitch, panning and key zones for each of the Timbres may be defined. Here also may be set filters to enable or disable each Timbre's response to certain MIDI message types, such as pitch‑bend or expression. Velocity curve is also adjustable here, or can take on the Global curve setting. One useful feature in the SG‑Rack's armoury is its use of 'macros' to quickly set up a pair of Timbres for split, layered, or velocity‑switching, saving you the painstaking effort of making all the necessary edits manually — a facility I'd like to see more of in the future please, Korg! In a similar fashion to Programs, a Performance may be named and saved, or the factory settings retrieved should it all go horribly wrong.

Korg have endowed the SG‑Rack with two effects processors (FX1 and FX2), arranged in series, and both capable of a wide range of useful treatments, including reverb, delay, flanging, chorus, overdrive and rotary speaker simulation. These effects are quite simply excellent, with the usual proviso that digital overdrive just never seems to get close to sounding like the real thing. In Performance mode, there is the flexibility to specify whether or not Timbre B should pass through FX1, which makes up somewhat for losing Timbre B's dedicated effects settings. The SG‑Rack's effects can be muted instantly by the single click of a button — no need to go searching through buried menus.

Global mode hides all of those useful goodies that affect the instrument as a whole, such as tuning, transposition and MIDI channel settings. Here also are the pages for transmitting MIDI System Exclusive data, and even a facility for customising the text message that appears when the SG‑Rack is first powered up — room for some fun here!

You Hum It...

So much for the theory. How does it all hang together in use? Well... very well, in fact. The generous 64‑voice polyphony is comforting. Selecting a stereo Program reduces this figure to a respectable 32 voices, but despite all my concerted efforts I couldn't make voice‑stealing an audible problem. The piano samples are generally superb, although just one or two of the sample changeover points are more obvious than I would have liked. The bottom ends of the pianos are rich and rounded, and the upper middle range — often gritty and cold on some other manufacturers' emulations — is deliciously clear and vibrant here. Several variants on the basic piano sound are served up, from bright, chunky dance pianos to smooth, warm concert grands. All acquitted themselves impressively. To be honest, I found it difficult to stray very far from Program A01 'Concert', which is pretty much all I've ever looked for in a sampled grand — smooth and vibrant, with plenty of sustain.

The SG‑Rack's electric pianos are equally inspiring, with plenty of character and warmth in the lower reaches of the keyboard. I still hate the velocity‑switching to which manufacturers resort to access the 'hard' electric piano samples, but until physical modelling comes up with a smooth‑changing alternative I guess we're stuck with it. The organs are amongst the best I've heard from any synth. The 'SGX Organ' Program held my attention for a long time, despite a rather too obvious tonal change in the middle of the keyboard. Selecting another Program, I was unprepared for such beautifully lush strings, and had to check my Kurzweil K2000 for a while to make sure I wasn't MIDI'd up somewhere I shouldn't be — impressive!

In any group of preset sounds there have to be a couple of duffers, and I could certainly live without the cheesy synth‑brass and bass, but they will undoubtedly find use in someone's music. I particularly missed a Yamaha CP70 emulation, although I guess I'm probably in a minority here (although in the good company of Peter Gabriel and Simple Minds, I'd hasten to add).


We are well past the days when a vague stab at a piano sound is considered adequate, and most players are keen to have at least one high quality piano sample amongst their armoury. Why replace your favourite master keyboard when you can just plug in a new set of piano samples? Studios looking to provide their clients with instant high‑quality piano timbres should definitely check out this device, and it will use up a mere 1U of studio rack space. In my opinion, the only other piano module that comes close to the SG‑Rack is probably General Music's RealPiano, which uses physical modelling to generate some of the resonances and nuances of the real thing — and to good effect.

The SG‑Rack is a solid purveyor of high‑quality piano (and piano related) sounds and more than up to the task. The non‑piano sounds are all very usable and only serve to make the package more tempting. Until someone comes up with a better way of doing the job, the SG‑Rack is about as good as it gets.

Spec Check

Synthesis type:AI2 synthesis
Voices:64 for mono Programs, 32 for stereo Programs
Waveform memory:24Mb
User memory:64 Programs, 64 Performances
Effects:2 digital multi‑effects units, supplying 12 effects types (reverb, early reflection, stereo delay, stereo chorus, stereo flanger, overdrive, stereo phaser, rotary speaker, auto pan, wah, flanger‑delay, hyper enhancer)
Connections:MIDI (In, Thru, Out), Output (L(Mono)/R), Phones
Display:20 character x 2 line backlit LCD
Dimensions:19 (W) x 10.4 (D) x 1.75 (H) inches


  • Quality piano sounds.
  • Plenty of other usable sounds.
  • Convenient, well‑built package.


  • Limited editing for some of the more synthetic sounds on offer.
  • Price could put some potential buyers off.


Delivers the goods as far as piano sounds are concerned and packs a lot of other usable sounds into the bargain. Price might be considered a little steep for some, but quality always comes at a price.